but有以下3种词性(你给出句子中but就是第2种以上，仅仅）

(1)conj. 但是；而是；然而

The watch was cheap, but it goes quite well.
这块表虽然便宜,但走得很好。

These changes will cost a lot, but they will save us money in the long run.
这些改动相当花钱,但从长远的角度看会为我们省钱。

(2)adv. 仅仅，只(相当于副词only,merely)

Our world is but a small part of the cosmos.
我们的世界仅仅是宇宙的一小部分而已。

He's still but a child.
他仅仅是个小孩子。

He can but admit that it was his fault.

他只得承认这是他的错误。

(3)prep. 除…以外

We go to school every day but Sunday.
我们除了星期日每天都上学。

He has looked for it everywhere but in his own room.
除了他自己的房间外,他到处都找遍了。

We go to school every day but Sunday.
我们除了星期日每天都上学。

He has looked for it everywhere but in his own room.
除了他自己的房间外,他到处都找遍了。

I had no choice but to sign the contract. 

我别无选择，只好签了合同。