1. To put or to attach something before or in front of another element: When Joe Rogers completed his medical training, he was allowed to prefix his name as "Dr. Joe Rogers".

The author wrote a preface which was prefixed at the beginning of his book.

2. To settle or to arrange in advance: The manager of the store in New York made sure his employees prefixed the items with the correct $ amount and the ¢ suffix when it was applicable, for example when a shirt was on sale for $5.50¢ (5 dollars and 50 cents).
3. In grammar and vocabulary, to add part of a word to the front of another a word: To prefix "dis" in front of "believe" results in "disbelieve".