An infix is a type of affix that is inserted within a word, rather than at the beginning or end. Infixes are less common than prefixes and suffixes, but they can be found in some languages. For example, in the Tagalog language, the infix "-um-" can be added to a root word to indicate a completed action. Infixes serve various grammatical functions, such as altering tense or aspect. They can also change the meaning of a word or create new forms. While infixes are not prevalent in English, they play a significant role in the morphology of languages like Arabic and Bontoc.