In linguistics, a simulfix is a type of affix that changes one or more existing phonemes (usually vowels) in order to modify the meaning of a morpheme.
Examples of simulfixes in English are generally considered irregularities, surviving results of Germanic umlaut. They include:
The transfixes of the Semitic languages may be considered a form of discontinuous simulfix.
In Javanese and colloquial Indonesian, simulfixation productively occurs to form active verbs and to derive verbs from noun bases. For example: