General Definition:
* A prefix is a word part added to the beginning of a word to change its meaning or create a new word.
More Detailed Definitions:
* A prefix is a morpheme (a meaningful unit of language) that is attached to the beginning of a word, creating a new word with a different meaning.
* A prefix is a bound morpheme (a meaningful unit that cannot stand alone as a word) that is added to the beginning of a word to alter its meaning.
Examples:
* un- in "unhappy" (means "not")
* pre- in "pregame" (means "before")
* multi- in "multitasking" (means "many")
Key Takeaways:
* Prefixes modify the meaning of a word.
* Prefixes are added to the beginning of a word.
* Prefixes are bound morphemes, meaning they can't stand alone as words.
Ultimately, the "best" definition depends on your specific needs and audience.