Which term refers to the smallest unit of sound that has meaning within a language?

The term that refers to the smallest unit of sound that has meaning within a language is "phoneme." Phonemes are the basic building blocks of spoken language, and they can change the meaning of a word when altered. For example, the difference between the words "bat" and "pat" is a matter of a single phoneme; changing the initial sound from /b/ to /p/ produces a different word with a different meaning.

In the context of phonetics, phonemes are abstract representations of sounds that can be realized as various pronunciations, depending on the linguistic environment. This is distinct from phones, which are actual sound units produced in speech without regard to meaning. Although phonetic units refer to similar concepts, they do not specifically denote the meaningful aspect that phonemes do. Allophones represent different variations of a phoneme that occur in specific contexts but do not change the meaning of the word, emphasizing the phoneme's role as the meaningful unit.