slow down vs detain

slow down and detain both are verbs.

Word	Noun	Adjective	Verb	Adverb
slow down	No	No	Yes	No
detain	No	No	Yes	No

As verbs, detain is a hyponym of slow down; that is, detain is a word with a more specific, narrower meaning than slow down:

Other hyponyms of slow down include slow, slow down, slow up, delay, hold up.

slow down (verb)	detain (verb)
become less tense, rest, or take one's ease	cause to be slowed down or delayed
lose velocity; move more slowly	stop or halt
become slow or slower	deprive of freedom; take into confinement
reduce the speed of
cause to proceed more slowly