Which of the following best describes a phoneme?

A phoneme is defined as the smallest unit of sound in a spoken language that can change the meaning of a word. For example, changing the initial phoneme in the word "bat" to a different sound such as "c" creates the word "cat," which has a completely different meaning. This ability to differentiate meaning through sound is a core feature of phonemes.

The other choices do not accurately represent a phoneme. A full word’s meaning refers to the understanding derived from a complete word, which encompasses more than just its phonetic sounds. A combination of letters typically refers to graphemes, which are the written symbols used to represent sounds in a language, rather than the sounds themselves. A written representation describes how words are visually depicted in writing, rather than focusing on the individual sounds that distinguish meaning. The focus on sound and meaning makes the correct choice central to the understanding of phonemes in language.