sidelight vs light source

sidelight and light source both are nouns.

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

As nouns, light source is a hypernym of sidelight; that is, light source is a word with a broader meaning than sidelight:

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
light source: any device serving as a source of illumination

Other hypernyms of sidelight include light.

sidelight (noun)	light source (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	any device serving as a source of illumination