traffic signal vs stoplight

traffic signal and stoplight both are nouns.

Word	Noun	Adjective	Verb	Adverb
traffic signal	Yes	No	No	No
stoplight	Yes	No	No	No

As nouns, traffic signal and stoplight are synonyms defined as:

traffic signal and stoplight: a visual signal to control the flow of traffic at intersections

Other synonyms of traffic signal include traffic light.

traffic signal (noun)	stoplight (noun)
a visual signal to control the flow of traffic at intersections	a visual signal to control the flow of traffic at intersections
	a red light on the rear of a motor vehicle that signals when the brakes are applied to slow or stop