What is defined as the smallest unit of speech sound?

The smallest unit of speech sound is known as a phoneme. Phonemes are the individual sounds that make up words and are foundational in the study of phonetics and phonology. They serve as building blocks for spoken language and differentiate meaning between words. For instance, changing the first phoneme in the word "bat" to another phoneme creates a completely different word such as "cat."

Understanding phonemes is crucial for developing phonemic awareness, which is essential for learning to read and write effectively. By recognizing and manipulating these units of sound, learners can decode written language, influencing their ability to read fluently and understand the intricacies of communication.

Other concepts such as words, syllables, and morphemes represent larger structures of language. A word consists of one or more morphemes, which are the smallest units of meaning rather than sound. A syllable is a unit of pronunciation that typically contains a vowel sound and may include surrounding consonants, but it is larger than a phoneme. Thus, the role of phonemes is distinctly separate, making them the correct answer to this question.