They are not the same. He likes sweets but[yet] he can't have it as he's diabetic. Though[despite] he's diabetic he doesn't stay away from sweets. Clear?

They are similar but they do not have the same meaning. They are both conjuctions: I forgot the name for "but", I think "though" is a subordinating conjunction. But is used for contrast: - I don't know you but I like you - You are handsome but you need a shower Though is typically used in spoken language and it's a fairly casual form. In the States, you'll usually find it at the end of a sentence but it can separate the two clause as well, just like "but". You could say that "though" introduces a challenge or an obstacle to whatever is in the first clause. The closest replacement for "though" that I can think of is "despite this". - I was in love with him for years. I can't stand him now, though. - I enjoyed the massage, though it hurt my lower back a little. (same as although)