What defines a morpheme?

A morpheme is defined as a meaningful linguistic unit, which is the essence of its function in language. It can be a whole word, such as "cat," or a prefix or suffix, such as "un-" in "unhappy" or "-s" in "cats." What distinguishes a morpheme is its ability to convey meaning; it cannot be further divided into smaller meaningful components without losing its significance.

Understanding that a morpheme serves as the building block of words helps in analyzing word formation and structure in any given language. This definition implies that morphemes can be free, able to stand alone as words, or bound, needing to attach to other morphemes to convey meaning. The other options, while related to language, do not capture the essence of what a morpheme is: they do not directly address its function as a unit of meaning.