What term encompasses the entire structure of a language, including its rules?

The term that encompasses the entire structure of a language, including its rules, is grammar. Grammar is the overarching framework that includes phonetics (sounds), phonology (sound systems), morphology (the structure of words), syntax (the arrangement of words into sentences), and semantics (meaning). It provides the guidelines for how words and phrases can be combined to create coherent and meaningful communication.

While other options like semantics refer specifically to meaning, pragmatics focuses on the context and implications of language use, and lexicon pertains to the vocabulary of a language, none of these encapsulate the complete set of rules governing language structure as grammar does. Thus, grammar is essential to understanding not only how language is formed but also how it functions in communication.