delay vs slowdown

delay and slowdown both are nouns.

Word	Noun	Adjective	Verb	Adverb
delay	Yes	No	Yes	No
slowdown	Yes	No	No	No

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

delay: the act of delaying; inactivity resulting in something being put off until a later time
slowdown: the act of slowing down or falling behind

delay (noun)	slowdown (noun)
the act of delaying; inactivity resulting in something being put off until a later time	the act of slowing down or falling behind
time during which some action is awaited

delay (verb)	slowdown (verb)
cause to be slowed down or delayed
stop or halt
slow the growth or development of
act later than planned, scheduled, or required