Collocations for mask - noun

face | gas | oxygen | surgical | Hallowe''en

have on, wear | put on | pull off, remove, strip off, take off, tear off
In the second part of the play, the actors take off their masks.

cover sth

behind/beneath a/the ~
Two eyes glared at him from beneath the mask.

in a/the ~
two men in black masks

~ over
She wore a mask over her face.

blank, cold, expressionless, grim, rigid
Her face was a blank mask as she answered my question.

slip
For a moment her mask slipped, and I saw how scared she really was.

behind a/the ~
Behind the mask of friendliness, I know he really dislikes me.

~ for
His fooling around is a mask for his lack of confidence.