An infix is an affix inserted inside a word stem (an existing word). It contrasts with adfix, a rare term for an affix attached to the end of a stem, such as a prefix or suffix.
When marking text for interlinear glossing, most affixes are separated with a hyphen, but infixes are separated with ⟨angle brackets⟩.
Read more about Infix: English, Similar Processes, Glossing