If you can’t say it in your own words, you just have someone else’s words in your notebook.

Copying a definition moves ink from one page to another without anything passing through you. Your own words are the test, because putting an idea into them forces you to decide what it actually claims, and the places where you stumble are the exact places you do not understand yet. Neat notes can hide that completely.

After each class, close everything and write three sentences about what happened in it, in the language you would use with a friend. The sentences that come out vague are your homework. Go back to those and nothing else.