Which of the following best describes a bound morpheme?

A bound morpheme is best described as a prefix or suffix that cannot stand alone. In linguistic terms, morphemes are the smallest units of meaning in a language. They can be classified as either free morphemes, which can stand alone as words (like "cat" or "run"), or bound morphemes, which need to attach to free morphemes to convey meaning. This includes elements such as prefixes (like "un-" in "undo") and suffixes (like "-ed" in "walked"). Bound morphemes enhance or modify the meaning of the words they are attached to but do not have independent usage.

To illustrate further: if you take a bound morpheme like "pre-" (as in "preview") or "-ing" (as in "running"), it cannot function independently. It relies on the root word to be meaningful, distinguishing it clearly from free morphemes that can exist alone.

This understanding of bound morphemes is essential in the study of language structure, particularly in understanding how words are formed and modified in various languages.