but
Definitions
Used to introduce a phrase or clause contrasting with what has already been mentioned.
Used to indicate the impossibility of anything other than what is being stated.
Used to introduce an added statement, typically one that is surprising or contrary to expectation.
Examples
I wanted to go for a walk, but it started to rain.
She studied hard for the exam, but she still felt nervous.
The cake looked delicious, but it tasted a bit too salty.
Synonyms
however nevertheless yet although still conversely nonetheless