Technical term used in mathematics, logic, and formal systems to denote a symbol representing an unspecified value or element.
In this expression, x and y are variables.
In logic, variables are treated as symbols that do not denote specific objects.
bound variable
Compound of 変 (hen, 'change') and 項 (kō, 'term' or 'item'), likely coined as a technical translation of 'variable' in logic and mathematics.