1: to state or declare positively and often forcefully or aggressively. 2 a: to demonstrate the existence of b: posit, postulate
Five cent word, maybe a little more.
More specific than:
This word combines statements of fact with resolve, belief and some amount of courage. It's a particular kind of stating or declaring but more general than avowing (closest ten cent synonym?) It is not a synonym for said, unfortunately.
It tends toward the abstract side, because it can involve action -- a lot of action, even, the nation asserted its sovereignty -- so it's not a word to use in a detailed action sequence. At the same time, it is often used in situations where it's reduced to passivity because it's indicating complex, abstract actions involving, say, a lot of paperwork or dull meetings. It's an element of legalese. This company asserts its right to serve its shareholders.
Which is a shame, because it would be more fun to send a squad of armored knights on horseback to assert the king's right to enforce the law of the land.
It's got more oomph than declaring or professing. Affirming involves more faith, though one can assert things without proof. Asserting implies some sort of evidence to back up the claim -- or maybe violence.
What comes to your mind?