idle vs light

idle and light both are nouns.

Word	Noun	Adjective	Verb	Adverb
idle	Yes	Yes	Yes	No
light	Yes	Yes	Yes	Yes

As adjectives, idle and light are synonyms defined as:

idle (noun)	light (noun)
the state of an engine or other mechanism that is idling	any device serving as a source of illumination
	a device for lighting or igniting fuel or charges or fires
	the visual effect of illumination on objects or scenes as created in pictures
	the quality of being luminous; emitting or reflecting light
	merriment expressed by a brightness or gleam or animation of countenance
	mental understanding as an enlightening experience
	a particular perspective or aspect of a situation
	public awareness
	a visual warning signal
	an illuminated area
	a person regarded very fondly
	(physics) electromagnetic radiation that can produce a visual sensation
	having abundant light or illumination
	a condition of spiritual awareness; divine illumination

idle (adjective)	light (adjective)
not in action or at work	of comparatively little physical weight or density
silly or trivial	psychologically light; especially free from sadness or troubles
not in active use	not great in degree or quantity or number
lacking a sense of restraint or responsibility	of the military or industry; using (or being) relatively small or light arms or equipment
not having a job	(used of color) having a relatively small amount of coloring agent
not yielding a return	characterized by or emitting light
without a basis in reason or fact	(physics, chemistry) not having atomic weight greater than average
	of little intensity or power or force
	easily assimilated in the alimentary canal; not rich or heavily seasoned
	silly or trivial
	weak and likely to lose consciousness
	having little importance
	less than the correct or legal or full amount often deliberately so
	designed for ease of movement or to carry little weight
	moving easily and quickly; nimble
	(used of soil) loose and large-grained in consistency
	having relatively few calories
	(of sound or color) free from anything that dulls or dims
	(of sleep) easily disturbed
	marked by temperance in indulgence
	very thin and insubstantial
	casual and unrestrained in sexual behavior
	demanding little effort; not burdensome
	(used of vowels or syllables) pronounced with little or no stress
	intended primarily as entertainment; not serious or profound

idle (verb)	light (verb)
run disconnected or idle	introduce light into
be idle; exist in a changeless situation	start or maintain a fire in
	begin to smoke
	to come to rest, settle
	alight from (a horse)
	fall to somebody by assignment or lot; passed
	cause to start burning; subject to fire or great heat

idle (adverb)	light (adverb)
	with few burdens