running light vs sidelight

running light and sidelight both are nouns.

Word	Noun	Adjective	Verb	Adverb
running light	Yes	No	No	No
sidelight	Yes	No	No	No

As nouns, running light and sidelight are synonyms defined as:

running light and sidelight: light carried by a boat that indicates the boat's direction; vessels at night carry a red light on the port bow and a green light on the starboard bow

running light (noun)	sidelight (noun)
light carried by a boat that indicates the boat's direction; vessels at night carry a red light on the port bow and a green light on the starboard bow	light carried by a boat that indicates the boat's direction; vessels at night carry a red light on the port bow and a green light on the starboard bow