mis-

mis- says the action was done, but done wrong. kompreni gives miskompreni, to misunderstand; uzi gives misuzi, to misuse; kalkuli gives miskalkuli; fari gives misfari, to blunder. English speakers get this one free, since it behaves almost exactly like the English prefix, and the verb ending never changes.

The nuance is that mis- reports a mistake, not a moral judgement. Something clumsy or botched rather than wicked takes -aĉ-, and a plain denial takes ne, so ne kompreni is failing to understand at all while miskompreni is understanding the wrong thing. Nothing in the first thousand words uses the prefix, and mistero is a single root that has fooled many a beginner.