allege “宣称，断定”，指在无真实凭据情况下宣称，硬说
例句：
(无充分证据而)断言,宣称：
①It has been alleged that Jack stole the money.
有人声称钱是杰克偷的。
②A newspaper article alleged that the cabinet was going to resign.
一家报纸宣称内阁即将辞职。
(作为理由、借口或论据等)提出：
③She was late for the meeting and alleged that her watch was wrong.
她开会迟到了,说是因为手表不准。
affirm “断言，肯定”，指根据事实坚信不移地宣称，而且有可靠证据，任何时候都不动摇，有无可争辩之意
例句：
①I can affirm that no one will lose their job.
我可以肯定，谁都不会丢掉工作。
②The ministers issued an affirmation of their faith in the system.
部长们表示了对该体制坚定的信心。
assert “宣称，坚持”， 主观意味强，指自认为某事就是如此，而不管事实如何。
例句：
①She asserted that she was innocent.
她坚称自己清白无辜。
②He asserted his innocence of the crime.
他坚称自己无罪。
claim “声称，主张”，往往表示说话者反对或不同意某一观点，或指根据某种规定提出的要求或主张
例句：
①She claimed that the ring was stolen, not lost.
她声言那只戒指是被偷的,而不是遗失的.
②She claims to be a good pianist.
她声称是位优秀的钢琴家。
现在，allege, affirm, assert, claim 这四个词的区别，你是不是搞清楚了呢?如果还是有些模糊，建议你直接把这几个例句背下来，相信一定会对你记住这四者的区别有所帮助!
