What are prefixes in terms of word formation?

Prefixes are specifically defined as morphemes that are added to the beginning of a base word to alter its meaning. This addition can change the meaning of the word significantly without changing the base form of that word. For example, adding the prefix "un-" to the word "happy" transforms it into "unhappy," indicating a negation of the original meaning.

Understanding prefixes is crucial in vocabulary development and comprehension, as they help in deciphering the meanings of new words encountered in reading. While morphemes can also be found at the end of words (which would be suffixes) or in the middle of words, prefixes are specifically those that precede the root word. Additionally, prefixes do not necessarily change the tense of verbs, which is a function more associated with certain suffixes or verb conjugation methods.