trouble, problem, troubles

!! Trouble is usually an uncountable noun. Never say 'a trouble'

• He has caused me a lot of trouble (NOT troubles).

• Are you having trouble (NOT a trouble) with your car?

A problem is a specific thing that causes worry or difficulty

• My biggest problem is shyness.

• There were a lot of problems with his work.

• They're having problems in their marriage.

Your troubles are your worries

• Sit down here and forget your troubles (OR problems) for a minute.