To insert a morpheme inside an existing word.
To instill.
A morpheme that always appears between other morphemes in a word, such as -i- and -o- in English (i.e. an interfix).
A morpheme inserted inside an existing word, such as -bloody- in English.
To insert anything somewhere (especially between other things), such as an affix into a word. (Compare interpolate.)
To insert an extra month into a calendar for the same purpose. The Hebrew calendar has such a month.
To insert a substance between two or more molecules, bases, cells, or tissues.
To insert an extra leap day into a calendar in order to maintain synchrony with natural phenomena.