the use in inflection or derivation of an allomorph that is not related in form to the primary allomorph of a morpheme, as the use of better as the comparative of good.
Origin: 1275–1325; ME: supplementation, supplement < ML supplētiōn- (s. of supplētiō) a filling up, equiv. to supplēt(us), ptp. of supplēre to make complete, (sup-sup-+ plē-, s. of plēre to fill (see full1) + -tus ptp. suffix) + -iōn--ion
sup·ple·tion (sə-plē'shən) n.
Linguistics The use of an unrelated form to complete a paradigm, as the past tense went of the verb go, goes, going, gone.
[From Latin supplētus, past participle of supplēre, to supply; see supply.]