可是 / 但是 / 然而 / 不过【kěshì / dànshì / rán'ér / búguò】

可是, 但是, 然而 and 不过 all introduce a contrast, and all four open their clause, before the subject. They differ in register and in how hard they push against what came before.

不过 – a softer "but"

不过 adds a reservation without overturning what was said. It's spoken, and it is the polite way to disagree or to add a condition.

可是 and 但是

Both are full contrasts. 但是 is neutral and works in writing; 可是 is more spoken and can carry a complaint or regret. Either follows 虽然. The short form 但 is common in writing.

然而 – written turns

然而 belongs to essays, news and narrative. It often starts a new sentence after a full stop and turns a whole line of argument. 却 frequently follows later in the same clause, after the subject.

In a chat, 然而 sounds like a written text read aloud.

Placement

English "however" can come mid-sentence. These four can't follow the subject; to put the contrast after the subject, use 却.

• × 我但是不想去 → 但是我不想去
• × 他然而没来 → 然而他没来 / 他却没来