These words are comparable when they refer to causes, circumstances or motivations which are put forth in order to defend, explain or extenuate an action, viewpoint or the like. An excuse is an implicit admission of wrong, but it is offered as a full or partial justification of one’s actions. By contrast, an apology , in current usage, is an open admission that one has done wrong and is sorry for it. Whereas an excuse is a means of avoiding or mitigating the responsibility for one’s actions, an apology is the contrite recognition of that responsibility.

• His excuse for being late was that his train was delayed; He could only offer a frank apology for having forgotten about our dinner engagement.

Apology and apologia both originally implied the intent of clearly setting forth the grounds for some action, conviction or the like, which others consider wrong or improper. Apology is now seldom used in this sense, apologia being preferred.

• The purged Communist stoutly defended his revolutionary zeal and wrote a lengthy apologia in explanation of his allegedly counter-revolutionary ideas.

Alibi , in common usage, implies that an excuse is plausible rather than true. In legal use, however, the word means a plea by an accused person that he was elsewhere when the crime was committed. Even in other contexts, alibi does not invariably suggest dubiety.

• His alibi depended upon the eyewitness testimony of a taxi driver; a desperate, last-minute alibi intended to save him from the wrath of his father.