Fetching details from the dictionary...

claim; insistence; assertion; advocacy; emphasis; contention; opinion; tenet
彼の主張は正しいと思います。
I think his claim is correct.
彼は会議で自分の意見を主張した。
He asserted his opinion at the meeting.
自分の意見を主張することが大切だ。
It's important to assert your own opinion.