slowdown vs delay

slowdown and delay both are nouns.

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

As nouns, delay is a hypernym of slowdown; that is, delay is a word with a broader meaning than slowdown:

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

Other hypernyms of slowdown include holdup.

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

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