One meaning of screening is the investigation of a great number of something (for instance, people) looking for those with a particular problem or feature.

For example at an airport many bags are screened by x-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 to try to detect any which may contain weapons or explosives, and people are screened by passing through a metal detector

Metal detector

A metal detector is a device which responds to metal that may not be readily apparent.The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field...

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The investigation of a large population is related; the members of a population are filtered by a metaphorical, rather than physical, screen.
If only part of a population is screened, screening is equivalent to sampling in statistics

Sampling (statistics)

In statistics and survey methodology, sampling is concerned with the selection of a subset of individuals from within a population to estimate characteristics of the whole population....

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Important cases of screening include:

• in biology and medicine
  • Screening (microbiology), a technique used to selectively isolate the target microbial species from a vast community of microbes.
  • Screening (medicine)
    Screening (medicine)
    Screening, in medicine, is a strategy used in a population to detect a disease in individuals without signs or symptoms of that disease. Unlike what generally happens in medicine, screening tests are performed on persons without any clinical sign of disease....
    
    
    • Cancer screening
      Cancer screening
      Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, urine tests, other tests, or medical imaging. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment must be weighed against any harms.Universal screening, mass...
      
      
      • Cervical cancer screening
        Cervical screening
        Cervical screening is a way of preventing cervical cancer from developing, and diagnosing the disease at an early stage. In the USA, cervical screening is usually performed using the Pap test , though the UK screening programmes changed the screening method to liquid-based cytology in...
        
        
      • Prostate cancer screening
        Prostate cancer screening
        Prostate cancer screening is an attempt to identify individuals with prostate cancer in a broad segment of the population—those for whom there is no reason to suspect prostate cancer. There are two methods used: One is the digital rectal examination , in which the examiner inserts a gloved,...
        
        
      • Breast cancer screening
        Breast cancer screening
        Breast cancer screening refers to the medical screening of asymptomatic, apparently healthy women for breast cancer in an attempt to achieve an earlier diagnosis. The assumption is that early detection will improve outcomes...
        
        
  • Fetal screening
  • Newborn screening
    Newborn screening
    Newborn screening is the process by which infants are screened shortly after birth for a list of disorders that are treatable, but difficult or impossible to detect clinically. Screening programs are often run by state or national governing bodies with the goal of screening all infants born in the...
    
    
  • Genetic screen
    Genetic screen
    A genetic screen is a procedure or test to identify and select individuals who possess a phenotype of interest. A genetic screen for new genes is often referred to as forward genetics as opposed to reverse genetics, the term for identifying mutant alleles in genes that are already known...
    
    
  • Two-hybrid screening
    Two-hybrid screening
    Two-hybrid screening is a molecular biology technique used to discover protein–protein interactions and protein–DNA interactions by testing for physical interactions between two proteins or a single protein and a DNA molecule, respectively.The premise behind the test is the activation of...
    
    
  • High-throughput screening
    High-throughput screening
    High-throughput screening is a method for scientific experimentation especially used in drug discovery and relevant to the fields of biology and chemistry. Using robotics, data processing and control software, liquid handling devices, and sensitive detectors, High-Throughput Screening allows a...
    
    
  • High-content screening
  • Virtual screening
    Virtual screening
    Virtual screening is a computational technique used in drug discovery research. By using computers, it deals with the quick search of large libraries of chemical structures in order to identify those structures which are most likely to bind to a drug target, typically a protein receptor or...
    
    
• in security
  • Terrorist Screening Database
    Terrorist Screening Database
    The Terrorist Screening Database or TSDB is the central terrorist watchlist consolidated by the FBI's Terrorist Screening Center and used by multiple agencies to compile their specific watchlists and for screening. The list consists of 400,000 unique names and over 1,000,000 records as of...
    
    
  • Secondary Security Screening Selection
    Secondary Security Screening Selection
    Secondary Security Screening Selection or Secondary Security Screening Selectee, known by its acronym SSSS, is an airport security measure in the United States and Canada which selects passengers for additional inspection. This may also be known as Selectee, Automatic Selectee or the Selectee list...
    
    
  • Call screening
    Call screening
    Call screening is the process of evaluating the characteristics of a telephone call before deciding how or whether to answer it.Some methods may include:* listening to the message being recorded on an answering machine or voice mail...
    
    
• Screening (economics)
  Screening (economics)
  Screening in economics refers to a strategy of combating adverse selection, one of the potential decision-making complications in cases of asymmetric information...
  
  
• Mechanical screening
  Mechanical screening
  Mechanical screening, often just called screening, is the practice of taking granulated ore material and separating it into multiple grades by particle size....
  
  
• Screening of articles; selection of articles for a systematic review
  Systematic review
  A systematic review is a literature review focused on a research question that tries to identify, appraise, select and synthesize all high quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine...
  
  
• Screening (tactical), a technique in which one military unit provides cover
  Cover (military)
  In military combat, the concept of cover refers to anything which is capable of physically protecting an individual from enemy fire. This differentiates it from the similar concept of concealment, in that an object or area of concealment only affords the benefit of stealth, not actual protection...
  
   for another in terms of both physical presence and firepower.

Screening can also mean preventing access of something by some sort of barrier. Particular cases:

• Electric field screening
  Electric field screening
  Screening is the damping of electric fields caused by the presence of mobile charge carriers. It is an important part of the behavior of charge-carrying fluids, such as ionized gases and conduction electrons in semiconductors and metals....
  
  
• Electromagnetic shielding
  Electromagnetic shielding
  Electromagnetic shielding is the process of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive and/or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world' and to cables to isolate...
  
   in physics, the exclusion of electric, magnetic, or electromagnetic fields by a metallic screen or shield
• In atomic physics and chemistry, the screening effect
  Screening effect
  In solids, especially in metals and semiconductors, the electrostatic screening or screening effect reduces the electrostatic field and Coulomb potential of an ion inside the solid...
  
   or atomic shielding is the reduction of effective nuclear charge by intervening electron shells
• Screening (printing), a process that represents lighter shades as tiny dots, rather than solid areas, of ink by passing ink through a perforated screen
• Screening is a process stage when cleaning paper pulp

Other uses:

• Film screening
  Film screening
  A film screening is the displaying of a motion picture or film, generally referring to a special showing as part of a film's production and release cycle...
  
  , showing a film by projection onto a screen
• Test screening
  Test screening
  A test screening is a preview screening of a movie or television show before its general release in order to gauge audience reaction. Preview audiences are selected from a cross-section of the population, and are usually asked to complete a questionnaire or provide feedback in some form. Harold...
  
  
• Private screening
  Private screening
  A private screening refers to a screening of a commercially made film to a group of people somewhere other than one of their homes. The legal issues can be complex, as the rules and regulation vary from country to country.-United Kingdom:...
  
  

• Stochastic screening
  Stochastic screening
  Stochastic screening or FM screening is a halftone process based on pseudo-random distribution of halftone dots, using frequency modulation to change the density of dots according to the gray level desired...