parking brake vs emergency

parking brake and emergency both are nouns.

Word	Noun	Adjective	Verb	Adverb
parking brake	Yes	No	No	No
emergency	Yes	No	No	No

As nouns, parking brake and emergency are synonyms defined as:

parking brake and emergency: a brake operated by hand; usually operates by mechanical linkage

Other synonyms of parking brake include emergency brake, hand brake.

parking brake (noun)	emergency (noun)
a brake operated by hand; usually operates by mechanical linkage	a brake operated by hand; usually operates by mechanical linkage
	a sudden unforeseen crisis (usually involving danger) that requires immediate action
	a state in which martial law applies