turn vs down

turn and down both are nouns.

Word	Noun	Adjective	Verb	Adverb
turn	Yes	No	Yes	No
down	Yes	Yes	Yes	Yes

As nouns, down is a hyponym of turn; that is, down is a word with a more specific, narrower meaning than turn:

Other hyponyms of turn include move, start, starting, innings, attack, at-bat, bat, lead, ruff, trumping, trick, hole-in-one.

turn (noun)	down (noun)
the act of changing or reversing the direction of the course	(American football) a complete play to advance the football
the act of turning away or in the opposite direction	soft fine feathers
taking a short walk out and back	fine soft dense hair (as the fine short hair of cattle or deer or the wool of sheep or the undercoat of certain dogs)
a favor for someone	(usually plural) a rolling treeless highland with little soil
(game) the activity of doing something in an agreed succession
turning or twisting around (in place)
a short performance that is part of a longer program
a movement in a new direction
an unforeseen development
a circular segment of a curve
(sports) a division of a game during which one team is on the offensive
a time period for working (after which you will be relieved by someone else)

turn (adjective)	down (adjective)
	being or moving lower in position or less in some value
	filled with melancholy and despondency
	extending or moving from a higher to a lower place
	becoming progressively lower
	not functioning (temporarily or permanently)
	lower than previously
	shut
	being put out in a game of baseball
	understood perfectly

turn (verb)	down (verb)
twist suddenly so as to sprain	improve or perfect by pruning or polishing
change to the contrary	bring down or defeat (an opponent)
go sour or spoil	drink down entirely
pass into a condition gradually, take on a specific property or attribute; become	eat up completely, as with great appetite
undergo a transformation or a change of position or action	cause to come or go down
change color	shoot at and force to come down
become officially one year older
have recourse to or make an appeal or request for help or information to
direct at someone
shape by rotating on a lathe or cutting device or a wheel
let (something) fall or spill from a container
alter the functioning or setting of
cause (an object) to assume a crooked or angular form
to break and turn over earth especially with a plow
to change orientation or direction
cause to move around a center so as to show another side of
cause to move around or rotate
pass to the other side of
move around an axis or a center
to send or let go
cause to move along an axis or into a new direction
channel one's attention, interest, thought, or attention toward or away from something
get by buying and selling
accomplish by rotating
undergo a change or development
cause to change or turn into something different;assume new characteristics

turn (adverb)	down (adverb)
	spatially or metaphorically from a higher to a lower level or position
	away from a more central or a more northerly place
	paid in cash at time of purchase
	in an inactive or inoperative state
	to a lower intensity
	from an earlier time