rear light vs taillight

rear light and taillight both are nouns.

Word	Noun	Adjective	Verb	Adverb
rear light	Yes	No	No	No
taillight	Yes	No	No	No

As nouns, rear light and taillight are synonyms defined as:

rear light and taillight: lamp (usually red) mounted at the rear of a motor vehicle

Other synonyms of rear light include rear lamp, tail lamp.

rear light (noun)	taillight (noun)
lamp (usually red) mounted at the rear of a motor vehicle	lamp (usually red) mounted at the rear of a motor vehicle