legitimate vs. legal

Legitimate means something is in accordance with established rules or standards, 정당한/타당한 in Korean. The established rules could be law, but not always. So being legitimate could imply lawfulness depending on the context, but that is not always the case.

• BP's CEO, Tony Hayward, has said the company will pay all "legitimate claims," well beyond the $75 million. But lawmakers have grown wary of the company's assurances as BP and other companies involved in the Gulf disaster have engaged in finger-pointing and resisted handing over video of the blown well. They are also worried about how BP will define "legitimate." (New York Times, May 25, 2010)

Here, legitimate means justified/genuine/reasonable, but not legal. Lawmakers are concerned because what a legitimate claim is in the Gulf oil spill case is not clearly defined by law, giving BP room for arbitrary liability.

• Make sure that he is the legitimate owner of the property you are about to purchase, as many cases of falsification of documents have been reported recently.
  

In this case, you could assume that legitimate also means legal/lawful, as real estate transactions are governed by law in most cases. When someone is a legitimate property owner, he or she must have acquired the property in a lawful way.

The following are some examples you might want to remember:

• illegitimate child: child outside of marriage
  
• illegal child (x)

• legal immigrants: immigrants who are in a country legally
• legitimate immigrants (x)

• legitimate copy: a copy that is authentic, not fake
• legal copy: a copy made in accordance with the law

• legal concerns: concerns that are related to the law
• legitimate concerns: justifiable and reasonable concerns