What about prepositions and connectors (conjunctions)?
You know, I find it more useful 3 or 4 examples than a big explanation. So, if you fill a lesson with examples that would be great, because that's really when I associate the word with its meaning.
And if you can add examples where
not to use a word that would most amazing thing on Earth.
Anyway it's your time, I don't want anyone to make such an effort if he later thinks that it was a waste of time. I appreciate what you do, what I said is only a suggestion.