Complementare

Complementare is a Romanian adjective meaning that serves to complete or improve something else. It is used to describe relations where two elements fit together to form a whole or to increase each other’s effectiveness. In mathematics and logic, the term often appears in the concept of a complement: for a given universal set U and a subset A, the complement A^c is the part of U not in A. The complement operation is central to Boolean algebra and logic, and it obeys De Morgan’s laws.

In probability, the complement of an event A is the event that A does not occur; the probability of A^c is 1 minus P(A). In economics, complementary goods are pairs of products that are often consumed together, such that demand for one increases demand for the other.

In biology and chemistry, complementarity describes a matching or compatibility between molecules or structures, such as DNA base pairing or the fit between an enzyme and its substrate, or antigen-antibody recognition. In linguistics and grammar, complementarity may refer to elements that complete a clause or phrase, though the term is less standard.

The word derives from Latin complementum and is used across disciplines to highlight relationships in which parts complete a system.