What best describes affixes in language?

Affixes are indeed best described as fixed word parts added to modify meanings. This definition captures the essence of what affixes do in the structure of language. Affixes can be either prefixes or suffixes, which are specific elements added to the beginning or end of a base word to alter its meaning or grammatical function. For example, adding the prefix "un-" to the word "happy" changes its meaning to "not happy," showcasing how affixes expand the versatility of the language by allowing us to create new words or change the meaning of existing ones. This understanding is foundational in studying morphology, the branch of linguistics concerned with the structure of words.

The other choices misrepresent the function of affixes. Some refer to complete words or limit the definition to only prefixes, which is not comprehensive enough to define all affixes. Others suggest that affixes lack grammatical function, which contradicis their fundamental role in word formation and meaning modification.