buy time vs detain

buy time and detain both are verbs.

Word	Noun	Adjective	Verb	Adverb
buy time	No	No	Yes	No
detain	No	No	Yes	No

As verbs, detain is a hypernym of buy time; that is, detain is a word with a broader meaning than buy time:

buy time: act so as to delay an event or action in order to gain an advantage
detain: cause to be slowed down or delayed

Other hypernyms of buy time include delay, hold up.

buy time (verb)	detain (verb)
act so as to delay an event or action in order to gain an advantage	cause to be slowed down or delayed
	stop or halt
	deprive of freedom; take into confinement