In language, what term is used to describe the complete set of spoken words?

The term that describes the complete set of spoken words in a language is lexicon. The lexicon encompasses all the vocabulary of a language, including the words and their meanings. It is akin to a mental dictionary that speakers use to understand and produce language.

In contrast, syntax refers to the rules and structures that govern how words combine to form sentences. Grammar encompasses the larger system that includes syntax as well as the rules of word formation, punctuation, and sentence structure, but it is not limited to the collection of words themselves. Dialect refers to a specific form of a language that is particular to a certain region or social group, and while it may have its own lexicon, it does not represent the entirety of spoken words in a language. Thus, lexicon is the correct term when defining the complete set of spoken words.