c.1500, "to make into one," from Middle French unifier (14c.), from Late Latin unificare "make one," from Latin uni- "one" (see uni-) + root of facere "to make" (see factitious). Related: Unified; unifying. Unified (field) theory in physics is recorded from 1935.
The unifier of a set of expressions is a set of substitutions of terms for variables such that the expressions are all equal.
See also most general unifier, unification.
(1994-12-06)