Here’s an informal writing prompt that will let you see whether students know what you mean when you talk about the function of some grammatical or punctuation term.
When we talk about grammar and punctuation, we often use the term function. In no more than three sentences, explain the meaning of function. To make your explanation clear, give an analogy to the function or functions of some physical object. You have 90 seconds to write.
This simple prompt will let you know whether students understand the terms you expect them to know. If they don’t understand the terms you’re using, you need to teach those terms as vocabulary.