What do phonotactic rules in English refer to?

Phonotactic rules in English refer to the legal combinations of sounds that can occur within a word or syllable in the language. These rules dictate which sound sequences are permissible and which are not, shaping the phonological structure of the language. For example, in English, the combination of sounds typically allowed at the beginning of a word includes consonants like /st/, as in "stop," but not a sequence like /tl/, which does not occur in standard English phonotactics.

Understanding the phonotactic rules is essential for recognizing how sounds can cluster together in natural speech, influencing accurate pronunciation and comprehension. These rules are distinct from aspects like stress patterns, grammatical structure, or pitch variations, which pertain to different linguistic elements such as prosody, syntax, and intonation, respectively. Therefore, the focus on sound combinations specifically aligns with the definition of phonotactic rules, thereby making it the correct answer to the question.