If something is self-evident, it is clearly true on its own. You should not need a pile of proof, a lecture, or a clever argument. The fact is supposed to show itself. The word is rather formal. You meet it in essays, law, and speeches more than in the kitchen. The famous American line “We hold these truths to be self-evident” is where many learners first see it, and it still has that civic, slightly grand sound. In looser talk people just say “obvious” or “of course.” Though actually, calling something self-evident can also be a power move: it shuts the door on questions. What is “clearly true” to one group is not always clear to another, so the word names a claim about proof, not a magic stamp that ends all disagreement.