What are the smallest units of spoken language that can change the meaning of a word?

The smallest units of spoken language that can change the meaning of a word are phonemes. Phonemes are the individual sounds that make up words, and altering one phoneme can lead to a completely different word with its own meaning. For example, changing the initial sound in "bat" from /b/ to /c/ changes it to "cat," which has a different meaning entirely.

In contrast, while syllables are larger units of sound than phonemes and do contribute to word formation, they do not individually change the meaning on their own; rather, they serve as a framework for how words are constructed. Morphemes, although they are meaningful units that can change the meaning of a word, are not limited to spoken language as they include prefixes, suffixes, and root words in both spoken and written forms. Vowels, while essential components of phonemes and syllables, do not stand alone as units that can independently alter meaning. Thus, phonemes are the most fundamental sound units that impact meaning in language.