What is a prefix?

A prefix is defined as an affix added before a word, which alters the meaning of the base word to which it is attached. For example, the prefix "un-" can be added to the word "happy" to create "unhappy," indicating the opposite meaning. Understanding prefixes helps in expanding vocabulary since many English words are formed by adding prefixes to root words.

In contrast, the other options describe different linguistic concepts. An affix added at the end of a word is known as a suffix, which has a different function in word formation. A type of phonics instruction method refers to a teaching strategy related to literacy, while a word that describes a noun is typically an adjective. Therefore, the correct definition clearly highlights the specific role of prefixes in modifying meanings in language.