expression

the act of saying what you think or showing how you feel using words or actions:

He wrote her a poem as an expression of his love.

We've received a lot of expressions of support for our campaign.

Freedom of expression is a basic human right.

It's better to give expression to (= show) your anger, rather than hiding it.

She plays the violin with great expression (= feeling).

the look on someone's face, showing what they feel or think:

I could tell from her expression that something serious had happened.

Mark always has such a miserable expression on his face.

a word or group of words used in a particular situation or by particular people:

He uses a lot of unusual expressions.

"A can of worms" is an expression that means "a difficult situation".