Nondualism is a term used to denote affinity, or unity, rather than duality or separateness or multiplicity. In reference to the universe it may be used to denote the idea that things appear distinct while not being separate. The term "nondual" (meaning "not two") can refer to a belief

Belief

Belief is the psychological state in which an individual holds a proposition or premise to be true.-Belief, knowledge and epistemology:The terms belief and knowledge are used differently in philosophy....

, condition, theory

Theory

The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...

, practice, or quality

Quality (philosophy)

A quality is an attribute or a property. Attributes are ascribable, by a subject, whereas properties are possessible. In contemporary philosophy, the idea of qualities and especially how to distinguish certain kinds of qualities from one another remains controversial.-Background:Aristotle analyzed...

. Nondualism has been linked with "Monism

Monism

Monism is any philosophical view which holds that there is unity in a given field of inquiry. Accordingly, some philosophers may hold that the universe is one rather than dualistic or pluralistic...

" or "qualified monism" with which it is sometimes confused (even conflated).
"Nondualism", "nonduality" and "nondual" are terms that have entered the English language from literal English renderings of "advaita

Advaita Vedanta

Advaita Vedanta is considered to be the most influential and most dominant sub-school of the Vedānta school of Hindu philosophy. Other major sub-schools of Vedānta are Dvaita and ; while the minor ones include Suddhadvaita, Dvaitadvaita and Achintya Bhedabheda...

" (Sanskrit: not-dual) subsequent to the first wave of English translations of the Upanishads commencing with the work of Müller

Max Müller

Friedrich Max Müller , more regularly known as Max Müller, was a German philologist and Orientalist, one of the founders of the western academic field of Indian studies and the discipline of comparative religion...

 (1823–1900), in the monumental Sacred Books of the East

Sacred Books of the East

The Sacred Books of the East is a monumental 50-volume set of English translations of Asian religious writings, edited by Max Müller and published by the Oxford University Press between 1879 and 1910...

(1879), who rendered "advaita" as "Monism

Monism

Monism is any philosophical view which holds that there is unity in a given field of inquiry. Accordingly, some philosophers may hold that the universe is one rather than dualistic or pluralistic...

" under influence of the then prevailing discourse of English translations of the Classical Tradition of the Ancient Greek

Ancient Greek

Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

s such as Thales

Thales

Thales of Miletus was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition...

  (624 BCE–c.546 BCE) and Heraclitus

Heraclitus

Heraclitus of Ephesus was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom...

 (c.535 BCE–c.475 BCE).