what is the definition for the prefix sim
A prefix is a syllable (or two) or a word added to a root/base with  that changes the word's meaning. A suffix is at the end.    Example:   Pregame (Pre=before so â¦ before the game)   Countable (able= can so can be counted).+ 60 others found this useful. Kayla Cash. prefix is a syllable (or two) or a word added to a root/base with  that changes the word's meaning. A suffix is at the end.    Example:   Pregame (Pre=before so â¦ before the game)   Countable (able= can so can be counted). + 60 others found this useful. Kayla Cash.