Which of the following best describes "affixes" in terms of word formation?

Affixes are linguistic elements that are attached to a root word to alter its meaning or grammatical function. This includes prefixes, which are added to the beginning of a word, and suffixes, which are added to the end. For instance, by adding the prefix "un-" to the root word "happy," it modifies the meaning to imply "not happy." Similarly, adding the suffix "-ness" to "happy" transforms it into "happiness," converting an adjective into a noun.

The other options do not accurately define affixes. Groups of root words do not encompass the concept of affixes, which are specific modifications to individual words. Specialized vocabulary pertains more to terminology within specific fields, which is unrelated to the structure of adding components to words. Words that express emotions are simply a category of words and do not represent the concept of affixes, which have a broader functional role in transforming meanings in various contexts.