disk brake vs disc brake

disk brake and disc brake both are nouns.

Word	Noun	Adjective	Verb	Adverb
disk brake	Yes	No	No	No
disc brake	Yes	No	No	No

As nouns, disk brake and disc brake are synonyms defined as:

disk brake and disc brake: hydraulic brake in which friction is applied to both sides of a spinning disk by the brake pads

disk brake (noun)	disc brake (noun)
hydraulic brake in which friction is applied to both sides of a spinning disk by the brake pads	hydraulic brake in which friction is applied to both sides of a spinning disk by the brake pads