heads-up vs alert

heads-up and alert both are nouns.

Word	Noun	Adjective	Verb	Adverb
heads-up	Yes	Yes	No	No
alert	Yes	Yes	Yes	No

heads-up (noun)	alert (noun)
a warning message	a warning serves to make you more alert to danger
	an automatic signal (usually a sound) warning of danger
	condition of heightened watchfulness or preparation for action

heads-up (adjective)	alert (adjective)
fully alert and watchful	engaged in or accustomed to close observation
	mentally perceptive and responsive
	quick and energetic

heads-up (verb)	alert (verb)
	warn or arouse to a sense of danger or call to a state of preparedness