Collocations for collar - noun

open, undone
His tie was knotted below his open collar. | His collar was undone.

button-down, turned-down | tight | starched, stiff | detachable | coat, shirt, etc. | high, stand-up, wing | clerical, dog
The vicar had his dog collar on.

have
The shirt had a button-down collar.

have on, wear | button, do up, fasten | unbutton, undo, unfasten | raise, turn up
She turned up her coat collar for extra warmth.

turn down | loosen

stud | size

collar and tie
He wore a collar and tie for the occasion.

dog | flea

have on, wear | slip
The dog slipped its collar and ran off.