Which of the following best describes phonemes?

Phonemes are defined as the smallest sound units in a language that can distinguish meaning between words. For instance, changing the phoneme /b/ in "bat" to /c/ results in the word "cat," illustrating how phonemes function as key units of sound that contribute to the differences in word meanings. This understanding is foundational for language instruction, especially for English learners, as it highlights the importance of sound discrimination in developing reading and speaking skills.

The other options describe different linguistic concepts. For example, the notion of single words conveying meaning relates more to vocabulary and semantics, while representing entire sentences aligns with syntax or grammar structures. Complex sentences involve multiple clauses and are relevant to sentence structure rather than phonemic understanding. Thus, the correct description of phonemes emphasizes their role as fundamental sound units critical for language development.