A binary opposition (also binary system) is a pair of related terms or concepts that are opposite in meaning. Binary opposition is the system by which, in language and thought, two theoretical opposites are strictly defined and set off against one another. It is the contrast between two mutually exclusive terms, such as on and off, up and down, left and right. Binary opposition is an important concept of structuralism, which sees such distinctions as fundamental to all language and thought. In structuralism, a binary opposition is seen as a fundamental organizer of human philosophy, culture, and language.
Binary opposition originated in Saussurean structuralist theory. According to Ferdinand de Saussure, the binary opposition is the means by which the units of language have value or meaning; each unit is defined in reciprocal determination with another term, as in binary code. It is not a contradictory relation but a structural, complementary one. Saussure demonstrated that a sign's meaning is derived from its context (syntagmatic dimension) and the group (paradigm) to which it belongs. An example of this is that one cannot conceive of 'good' if we do not understand 'evil'.
Typically, one of the two opposites assumes a role of dominance over the other. The categorization of binary oppositions is "often value-laden and ethnocentric", with an illusory order and superficial meaning. Furthermore, Pieter Fourie discovered that binary oppositions have a deeper or second level of binaries that help to reinforce meaning. As an example, the concepts hero and villain involve secondary binaries: good/bad, handsome/ugly, liked/disliked, and so on.
A classic example of a binary opposition is the presence-absence dichotomy. In much of Western thought, including structuralism, distinguishing between presence and absence, viewed as polar opposites, is a fundamental element of thought in many cultures. In addition, according to post-structuralist criticisms, presence occupies a position of dominance in Western thought over absence, because absence is traditionally seen as what you get when you take away presence. (Had absence been dominant, presence might have most naturally been seen as what you get when you take away an absence.)
According to Nasser Maleki, there is another example of this phenomenon whereby people value one part of a binary opposition over another; “we, as living in a certain culture, think and act similarly in situations when we want to pick out one of the concepts in the binary oppositions or while seeking truth or a center. For example, we give superiority to life rather than death.” This suggests that the cultural setting a reader is a part of may influence their interpretation of a work of literature; “only one concept, from the binary opposition, is ready, in our mind, to be privileged and the other one is usually put aside as having the second priority.” He reached this conclusion by giving a name to the shared western unconsciousness for a preferred binary concept- logocentrism. This is the belief that “an ultimate reality or centre of truth exists and that can serve as the basis for all our thought and actions. This might imply that readers might unconsciously take side with one concept of binary opposition, and Derrida traces this reaction as a cultural phenomenon.”