Meaning of free variation

free' varia'tion

Pronunciation: [key]
— Ling. Ling.
  1. a relation between the members of a pair of phones, phonemes, morphs, or other linguistic entities such that either of the two may occur in the same position with no change in the meaning of the utterance: in the first syllable of “economics,” “e” and “ē” are in free variation. Cf. complementary distribution.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.