The shirt had a stiff white collar.

A piece of clothing worn around the neck, often as part of a shirt or jacket.
The dog wore a red collar.
Her dress had a lace collar.
He adjusted his shirt collar.
dog collar
shirt collar
button-down collar
neckband
ruff
band
The dog wore a red collar around its neck.

A band or strap that encircles the neck of an animal, typically used for control or restraint.
The cat's collar had a bell.
He put a new collar on the puppy.
The dog's collar was too tight.
dog collar
leather collar
tight collar
leash
harness
restraint