because of a possibility of something happening, being needed, etc.

I don't think I'll need any money but I'll bring some just in case. 我想我不会用到钱的，不过我还是要带一些以防万一。

Bring a map in case you get lost. 带张地图吧，以防迷路。

The forecast didn't mention rain but I'm going to take an umbrella just in case.

The guy in the red shirt, in case you were wondering, is Klara's husband.

Take a sandwich with you in case you get hungry on the train.

See also: case noun (SITUATION)