How is the term "phoneme" best defined?

The term "phoneme" is best defined as a single unit of sound in speech. Phonemes are the smallest segments of sound that can differentiate meaning in a language. For instance, in English, the words "bat" and "pat" differ by a single phoneme – the initial sounds /b/ and /p/. Understanding phonemes is crucial for phonemic awareness, which is foundational for developing reading and spelling skills. This significance is why "phoneme" refers specifically to sound, rather than visual representations (as might be suggested by a visual representation of a letter), methods for teaching literacy, or combinations of letters, which pertain to larger constructs in language and literacy development.