It can be compared to usage, which refers to the rules for making language and the structures we use to make it.
Example
One use of the third conditional is to express regret, e.g. ‘If I hadn't spent so much time mucking about at school, I would have passed a few more exams'.
In the classroom
A key stage in awareness of how English works is when learners understand that usage and use are not necessarily connected. For example, the past form of verbs (usage) can express a wish about the present (use), such as:
- I wish I didn't have this boss. He's awful!
Further links:
https://www.teachingenglish.org.uk/article/analysing-language