What is the smallest unit in a language that carries meaning?

The smallest unit in a language that carries meaning is the morpheme. Morphemes are the building blocks of words and can be whole words or parts of words, such as prefixes, suffixes, and root words. For instance, in the word "unhappiness," "un-" is a morpheme that indicates negation, "happy" is a morpheme that conveys the core meaning, and "-ness" is a morpheme that turns an adjective into a noun.

In contrast, phonemes refer to the individual sounds of a language, syllables are units of pronunciation that may contain one or more phonemes but do not themselves carry meaning, and words are made of one or more morphemes. Therefore, while words and syllables consist of morphemes, the morpheme itself is the essential unit that has semantic value.