but; however; although — a colloquial conjunction/particle used to show contrast or to soften/leave a sentence hanging.
昨日は行ったけど、あまり楽しくなかった。
I went yesterday, but it wasn't very fun.
その案はいいけど、予算が足りない。
That idea is good, but the budget isn't enough.
行くと言ったけど、まだ準備ができていない。
I said I'd go, but I'm not ready yet.
食べたいけど、今はダイエット中なんだ。
I want to eat it, but I'm on a diet right now.