Definition - A type of affix that changes one or more existing phonemes in order to modify the meaning of a morpheme.

1. The act of affixing a simulfix is called simulfixation.

Example -
louse --> lice

Etymology -
The term derives from the Latin simul, at the same time.

Oxford English Dictionary -
Its first citation is from 1954:
"The term ‘superfix’ is no more apt than ‘subfix’, and (the bad Latin) ‘simulfix’ might be even better."
(Word X. 212 )

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