The Greek alphabet is the script that has been used to write the Greek language since at least 730 BC . The alphabet in its classical and modern form consists of 24 letters ordered in sequence from alpha to omega...
Greek numerals are a system of representing numbers using letters of the Greek alphabet. They are also known by the names Ionian numerals, Milesian numerals , Alexandrian numerals, or alphabetic numerals...
lambda has a value of 30. Lambda is related to the Phoenician letter
Phoenician alphabet
The Phoenician alphabet, called by convention the Proto-Canaanite alphabet for inscriptions older than around 1050 BC, was a non-pictographic consonantal alphabet, or abjad. It was used for the writing of Phoenician, a Northern Semitic language, used by the civilization of Phoenicia...
An alphabet is a standard set of letters—basic written symbols or graphemes—each of which represents a phoneme in a spoken language, either as it exists now or as it was in the past. There are other systems, such as logographies, in which each character represents a word, morpheme, or semantic...
Ł or ł, described in English as L with stroke, is a letter of the Polish, Kashubian, Sorbian, Łacinka , Łatynka , Wilamowicean, Navajo, Dene Suline, Inupiaq, Zuni, Hupa, and Dogrib alphabets, several proposed alphabets for the Venetian language, and the ISO 11940 romanization of the Thai alphabet...
El is a letter of the Cyrillic alphabet.El commonly represents the alveolar lateral approximant , like the pronunciation of ⟨l⟩ in "lip".-Form:...
(Л, л). The ancient grammarians and dramatists give evidence to the pronunciation as laːbdaː in Classical Greek times. In Modern Greek
Modern Greek
Modern Greek refers to the varieties of the Greek language spoken in the modern era. The beginning of the "modern" period of the language is often symbolically assigned to the fall of the Byzantine Empire in 1453, even though that date marks no clear linguistic boundary and many characteristic...
the name of the letter, Λάμδα, is pronounced lamða; the spoken letter itself has the sound of [l] as with Latinate "L".
In early Greek alphabets, the shape and orientation of lambda varied. Most variants consisted of two straight strokes, one longer than the other, connected at their ends. The angle might be in the upper left, lower left ("Western" alphabets), or top ("Eastern" alphabets). Other variants had a vertical line with a horizontal or sloped stroke running to the right. With the general adoption of the Ionic alphabet, Greek settled on an angle at the top; the Romans, borrowing from Western alphabets, put the angle at the lower left.
The HTML 4 character entity references for the Greek capital and small letter lambda are "Λ" and "λ" respectively.
In mathematics, and more specifically set theory, the empty set is the unique set having no elements; its size or cardinality is zero. Some axiomatic set theories assure that the empty set exists by including an axiom of empty set; in other theories, its existence can be deduced...
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
, though other symbols are more commonly used, such as .
The Lambda baryons are a family of subatomic hadron particles which have the symbols, , and and have +1 elementary charge or are neutral. They are baryons containing three different quarks: one up, one down, and one third quark, which can be either a strange , a charm , a bottom or a top quark...
In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...
in subatomic particle physics.
Lambda is the set of logical axioms in the axiomatic method of logical deduction in first-order logic
First-order logic
First-order logic is a formal logical system used in mathematics, philosophy, linguistics, and computer science. It goes by many names, including: first-order predicate calculus, the lower predicate calculus, quantification theory, and predicate logic...
Sparta or Lacedaemon, was a prominent city-state in ancient Greece, situated on the banks of the River Eurotas in Laconia, in south-eastern Peloponnese. It emerged as a political entity around the 10th century BC, when the invading Dorians subjugated the local, non-Dorian population. From c...
n Army. This stood for Lakedaimon, the name of the region of Sparta.
In mathematics, the von Mangoldt function is an arithmetic function named after German mathematician Hans von Mangoldt.-Definition:The von Mangoldt function, conventionally written as Λ, is defined as...
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
, Wilks's lambda is used in multivariate analysis of variance (MANOVA
MANOVA
Multivariate analysis of variance is a generalized form of univariate analysis of variance . It is used when there are two or more dependent variables. It helps to answer : 1. do changes in the independent variable have significant effects on the dependent variables; 2. what are the interactions...
analysis) to compare group means on a combination of dependent variables.
In the spectral decomposition of matrices, lambda indicates the diagonal matrix
Diagonal matrix
In linear algebra, a diagonal matrix is a matrix in which the entries outside the main diagonal are all zero. The diagonal entries themselves may or may not be zero...
In mathematics, a matrix is a rectangular array of numbers, symbols, or expressions. The individual items in a matrix are called its elements or entries. An example of a matrix with six elements isMatrices of the same size can be added or subtracted element by element...
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, lambda is the time window over which a process is observed for determining the working memory set for a digital computer's virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
, lambda represents the likelihood that a small body will encounter a planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
A dwarf planet, as defined by the International Astronomical Union , is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite...
leading to a deflection of a significant magnitude. An object with a large value of lambda is expected to have cleared its neighborhood
Clearing the neighbourhood
"Clearing the neighbourhood of its orbit" is a criterion for a celestial body to be considered a planet in the Solar System. This was one of the three criteria adopted by the International Astronomical Union in its 2006 definition of planet....
The definition of planet, since the word was coined by the ancient Greeks, has included within its scope a wide range of celestial bodies. Greek astronomers employed the term asteres planetai , "wandering stars", for objects which apparently move over the sky...
Crystal optics is the branch of optics that describes the behaviour of light in anisotropic media, that is, media in which light behaves differently depending on which direction the light is propagating. The index of refraction depends on both composition and crystal structure and can be...
, lambda is used to represent the period of a lattice.
In NATO military operations, a chevron (a capital lambda symbol) is painted on the vehicles of this military alliance for identification. (The Spartan army
Spartan Army
The Spartan army was the military force of Sparta, one of the leading city-states of ancient Greece. The army stood at the centre of the Spartan state, whose citizens' primary obligation was to be good soldiers. Subject to military drill from infancy, the Spartans were one of the most feared...
Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...
, lambda denotes the "equivalent conductance" of an electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...
In physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...
.
In optics, lambda denotes the grating pitch of a Bragg reflector.
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
and radioactivity. This constant is very simply related (by a multiplicative constant) to the half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of any radioactive material.
In probability theory, lambda represents the density of occurrences within a time interval, as modeled by the Poisson distribution
Poisson distribution
In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time and/or space if these events occur with a known average rate and independently of the time since...
Mathematical logic is a subfield of mathematics with close connections to foundations of mathematics, theoretical computer science and philosophical logic. The field includes both the mathematical study of logic and the applications of formal logic to other areas of mathematics...
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
In programming language theory, an anonymous function is a function defined, and possibly called, without being bound to an identifier. Anonymous functions are convenient to pass as an argument to a higher-order function and are ubiquitous in languages with first-class functions such as Haskell...
In mathematical logic and computer science, lambda calculus, also written as λ-calculus, is a formal system for function definition, function application and recursion. The portion of lambda calculus relevant to computation is now called the untyped lambda calculus...
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....
(1 μL) or one cubic millimeter (1 mm3). This always rare use is currently deprecated.
Lambda indicates an eigenvalue in the mathematics of linear algebra
Linear algebra
Linear algebra is a branch of mathematics that studies vector spaces, also called linear spaces, along with linear functions that input one vector and output another. Such functions are called linear maps and can be represented by matrices if a basis is given. Thus matrix theory is often...
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
The linear, surface, or volume charge density is the amount of electric charge in a line, surface, or volume, respectively. It is measured in coulombs per meter , square meter , or cubic meter , respectively, and represented by the lowercase Greek letter Rho . Since there are positive as well as...
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
Multivariable calculus is the extension of calculus in one variable to calculus in more than one variable: the differentiated and integrated functions involve multiple variables, rather than just one....
One of several short channel effects in MOSFET scaling, channel length modulation is a shortening of the length of the inverted channel region with increase in drain bias for large drain biases...
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
Enterobacteria phage λ is a temperate bacteriophage that infects Escherichia coli.Lambda phage is a virus particle consisting of a head, containing double-stranded linear DNA as its genetic material, and a tail that can have tail fibers. The phage particle recognizes and binds to its host, E...
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
, lambda denotes the long-term intrinsic growth rate of a population. This value is often calculated as the dominant eigenvalue of the age/size class matrix (mathematics)
Matrix (mathematics)
In mathematics, a matrix is a rectangular array of numbers, symbols, or expressions. The individual items in a matrix are called its elements or entries. An example of a matrix with six elements isMatrices of the same size can be added or subtracted element by element...
.
In formal language theory and in computer science, lambda denotes the empty string
Empty string
In computer science and formal language theory, the empty string is the unique string of length zero. It is denoted with λ or sometimes Λ or ε....
In fiber-optic communications, wavelength-division multiplexing is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light...
Frequency-division multiplexing is a form of signal multiplexing which involves assigning non-overlapping frequency ranges to different signals or to each "user" of a medium.- Telephone :...
In measure theory, the Lebesgue measure, named after French mathematician Henri Lebesgue, is the standard way of assigning a measure to subsets of n-dimensional Euclidean space. For n = 1, 2, or 3, it coincides with the standard measure of length, area, or volume. In general, it is also called...
Set theory is the branch of mathematics that studies sets, which are collections of objects. Although any type of object can be collected into a set, set theory is applied most often to objects that are relevant to mathematics...
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
indicates the proportional reduction in error when one variable's values are used to predict the values of another variable.
An oxygen sensor, or lambda sensor, is an electronic device that measures the proportion of oxygen in the gas or liquid being analyzed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman...
Air–fuel ratio is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich...
in the exhaust gases of an internal-combustion engine.
Lambda is the name of a series of Japanese rockets. It consisted of the types Lambda 2, LS-A, LSC-3, Lambda 3, Lambda 4 and LS-C.On February 11, 1970 the first Japanese satellite Ōsumi was launched using a Lambda 4 rocket....
A booster rocket is either the first stage of a multi-stage launch vehicle, or else a strap-on rocket used to augment the core launch vehicle's takeoff thrust and payload capability. Boosters are generally necessary to launch spacecraft into Earth orbit or beyond...
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
Failure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. It is often denoted by the Greek letter λ and is important in reliability engineering....
Reliability theory describes the probability of a system completing its expected function during an interval of time. It is the basis of reliability engineering, which is an area of study focused on optimizing the reliability, or probability of successful functioning, of systems, such as airplanes,...
, and it is measured in failure events per hour. Numerically, this lambda is also the reciprocal of the mean time between failure
Mean time between failure
Mean time between failures is the predicted elapsed time between inherent failures of a system during operation. MTBF can be calculated as the arithmetic mean time between failures of a system. The MTBF is typically part of a model that assumes the failed system is immediately repaired , as a...
s.
In criminology, lambda denotes an individual's frequency of offenses.
In cartography and navigation, lambda denotes the longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
of a location.
Lambda is the symbol of the musician Richard D. James or Aphex Twin
Aphex Twin
Richard David James , best known under the pseudonym Aphex Twin, is an Irish-born electronic musician and composer described as "the most inventive and influential figure in contemporary electronic music"...
Christopher Langton is an American computer scientist and one of the founders of the field of artificial life. He coined the term in the late 1980s when he organized the first "Workshop on the Synthesis and Simulation of Living Systems" at the Los Alamos National Laboratory in 1987.Langton made...
Stephen Wolfram is a British scientist and the chief designer of the Mathematica software application and the Wolfram Alpha computational knowledge engine.- Biography :...
A cellular automaton is a discrete model studied in computability theory, mathematics, physics, complexity science, theoretical biology and microstructure modeling. It consists of a regular grid of cells, each in one of a finite number of states, such as "On" and "Off"...
Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
ic conductance of a given ion (The composition of the ion is generally shown as a subscript to the lambda character).
Length constant is a constant used in neurobiology signified by the Greek letter lambda . The longer a length constant is, the bigger the effect a potential will have along the cell...
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...
, lambda denotes the heat of vaporization per mole of material (a.k.a. its "latent heat").
In the technology and science of celestial navigation, lambda denotes the longitude as opposed to the Roman letter "L" which denotes the latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
Louis XIII was a Bourbon monarch who ruled as King of France and of Navarre from 1610 to 1643.Louis was only eight years old when he succeeded his father. His mother, Marie de Medici, acted as regent during Louis' minority...
used the letter lambda as his personal symbol rather than monogram
Monogram
A monogram is a motif made by overlapping or combining two or more letters or other graphemes to form one symbol. Monograms are often made by combining the initials of an individual or a company, used as recognizable symbols or logos. A series of uncombined initials is properly referred to as a...
AB Volvo is a Swedish builder of commercial vehicles, including trucks, buses and construction equipment. Volvo also supplies marine and industrial drive systems, aerospace components and financial services...
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s, lambda denotes an engine, fuel, or ignition system failure.
Lambda is used as a recurring symbol for the human resistance in the Valve computer game series Half-Life
Half-Life (series)
The Half-Life series of video games share a science fiction alternate history. Nearly all of the games are first-person shooters on the GoldSource or Source engines, and most are linear, narrative, single-player titles....
.
Lambda is used to connote homosexuality and as an international symbol of gay rights.
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
, lambda is an operator used to denote anonymous functions or closures
Closure (computer science)
In computer science, a closure is a function together with a referencing environment for the non-local variables of that function. A closure allows a function to access variables outside its typical scope. Such a function is said to be "closed over" its free variables...
In mathematical logic and computer science, lambda calculus, also written as λ-calculus, is a formal system for function definition, function application and recursion. The portion of lambda calculus relevant to computation is now called the untyped lambda calculus...
. An example of this use of lambda in the Python language is this section of computer code that sorts a list alphabet
Alphabet
An alphabet is a standard set of letters—basic written symbols or graphemes—each of which represents a phoneme in a spoken language, either as it exists now or as it was in the past. There are other systems, such as logographies, in which each character represents a word, morpheme, or semantic...
Unlambda is a minimal, "nearly pure" functional programming language invented by David Madore. It is based on combinatory logic, a version of the lambda calculus that omits the lambda operator. It relies mainly on two built-in functions and an "apply" operator...
In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state...
Combinatory logic is a notation introduced by Moses Schönfinkel and Haskell Curry to eliminate the need for variables in mathematical logic. It has more recently been used in computer science as a theoretical model of computation and also as a basis for the design of functional programming...
, a simplification of the lambda calculus that does not involve the lambda at all, hence the un- prefix.
An oxygen sensor, or lambda sensor, is an electronic device that measures the proportion of oxygen in the gas or liquid being analyzed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman...
(O2 sensor) is also known as a lambda probe, sensor, sond, or sonde.
Lambda is used in art and photography to refer to a digital Type C print
Type C print
Chromogenic color prints are full-color photographic prints made using chromogenic materials and processes. These prints may be produced from an original which is a color negative, slide, or digital image. The chromogenic print process, was nearly synonymous with the 20th century color snapshot...
, or to the equipment that is used to produce it.
Lambda was used by Pythagoras to denote the "Lambda number sequence" { 1, 2, 3, 4, 8, 9, 27, ... }.
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
Star Wars is an American epic space opera film series created by George Lucas. The first film in the series was originally released on May 25, 1977, under the title Star Wars, by 20th Century Fox, and became a worldwide pop culture phenomenon, followed by two sequels, released at three-year...
uses a transport vehicle known as the Lambda-class shuttle that when viewed forward has the shape of the lowercase lambda.
Lambda is occasionally used in graphic design to represent a stylised 'A'. Examples include the Disney movie Atlantis: The Lost Empire
Atlantis: The Lost Empire
Atlantis: The Lost Empire is a 2001 American animated film produced by Walt Disney Feature Animation. Written by Tab Murphy, directed by Gary Trousdale and Kirk Wise, and produced by Don Hahn, it is the first science fiction film in the Disney animated features canon and the 41st overall. The film...
Angels & Airwaves is an American alternative rock supergroup led by Blink-182 guitarist/vocalist Tom DeLonge, also including guitarist David Kennedy from Over My Dead Body, Hazen Street and Box Car Racer, bass guitarist Matt Wachter from 30 Seconds to Mars and former Lostprophets and Nine Inch...
Dream Theater is an American progressive metal band formed in 1985 under the name Majesty by John Petrucci, John Myung, and Mike Portnoy while they attended Berklee College of Music in Massachusetts. They subsequently dropped out of their studies to further concentrate on the band that would...
The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...
, and the logo of the engineering consultancy Atkins. Conversely, the name of the band Λucifer is sometimes spelled Aucifer.
Stargate SG-1 uses a modified upper-case lambda, with a small circle above the apex, to indicate Earth. This symbol has since become associated with the entire franchise.
Providence is the capital and most populous city of Rhode Island and was one of the first cities established in the United States. Located in Providence County, it is the third largest city in the New England region...
based musician Xavier Valentine.
The Half-Life franchise of video games uses an encircled lower-case lambda as the franchise logo (Half-Life 2 adds the numeral 2 into the logo as superscript), prominently featured on the chest of the protagonist's powered armor. In the first game, the logo appears at the entrances of the Black Mesa Research Facility's Lambda Complex which conducted teleportation research. In Half-Life 2 and its Episodes, the encircled lambda is the universal symbol of the Resistance, often spraypainted to mark the location of safehouses and hidden supply caches; full-time Resistance members wear armbands containing a lower-case lambda without the circle.
See also
Greek letters used in mathematics, science, and engineering
. Letters in other alphabet
.