There are significant differences in usage. Legitimate has an expanded use beyond law, essentially meaning "credible" or even "extreme" I didn't think Croatia was a legitimate contender for the World Cup, but they reached the finals. Is there a legitimate chance that Brexit will be reversed? My boss is a legitimate imbecile. "lawful" tends to be used in discussions of legality. Behaviors are "lawful" My conduct was lawful. (I didn't break the law) She is my lawfully wedded wife. (she married me according to the law) I believe the actions were unlawful. (I think the actions violated the law.) Legal is more colloquial. He's legal to drink. (He's reached the legal drinking age) (could not substitute lawful or legitimate) It's a legal issue. If you want good advice, call a lawyer.(could not substitute lawful or legitimate) Is it legal to set off fireworks in this town? (could use lawful but would sound odd. Couldn't use legitimate)

Legitimate = following the rules and laws Legal = Something that is permitted by law Lawful = Something that is permitted by law legal and lawful are the same but legitimate is a bit different. Being legitimate is the /action/ of following laws.

They are synonyms, although "legal" has a few more meanings based on context. Legal 1. of, based on, or concerned with the law. 2. permitted by law. 3. (of paper) measuring 8 ½ by 14 inches. Lawful 1. conforming to, permitted by, or recognized by law or rules.

That is a really good question. I had to look them up to make sure I understood the differences before I replied. And what I found out is they are synonyms of one another. A synonym is a word or phrase that means exactly or nearly the same as another