A symbol of a formal language used to denote an arbitrary element (individual) in the structure described by this language. Every formal language contains one or several types of individual variables, there being an infinite set of variables of each type. For example, the language of the theory of vector spaces contains two types of individual variables, namely for vectors and for scalars, while the language of arithmetic contains one type, namely for the non-negative integers.
See also Individual constant.
Individual variable. S.K. Sobolev (originator), Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Individual_variable&oldid=17515