What is the definition of a phoneme?

A phoneme is defined as the smallest unit of sound in a language. It represents the basic building blocks of speech that, when combined, create words and meanings. This sounds distinct from the other options, which focus on aspects of written language or syllable structure, rather than the auditory aspect of spoken language.

Phonemes are crucial for understanding linguistic structure because they can change the meaning of words when altered. For example, changing the initial phoneme in the word "bat" to "c" creates a completely different word, "cat." This underlines the significance of phonemes in both spoken language and the development of phonemic awareness, which is essential in reading and language acquisition.

In contrast, the other choices refer to different aspects of language:

• The smallest unit of writing pertains to graphemes, not phonemes.

• The longest syllable in a word does not relate to the definition of phoneme, as it does not describe sound units specifically.

• A written letter refers to individual characters in the alphabet, which is a different concept entirely from the auditory characteristics of phonemes.

Thus, option B accurately captures the essence of a phoneme as it relates directly to sound.