alert vs air alert

alert and air alert both are nouns.

Word	Noun	Adjective	Verb	Adverb
alert	Yes	Yes	Yes	No
air alert	Yes	No	No	No

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

alert: an automatic signal (usually a sound) warning of danger
air alert: the warning signal that begins a period of preparation for an enemy air attack

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

alert: condition of heightened watchfulness or preparation for action
air alert: the condition in which combat aircraft are airborne and ready for an operation

Other hyponyms of alert include red alert, strip alert.

alert (noun)	air alert (noun)
a warning serves to make you more alert to danger	the warning signal that begins a period of preparation for an enemy air attack
an automatic signal (usually a sound) warning of danger	the condition in which combat aircraft are airborne and ready for an operation
condition of heightened watchfulness or preparation for action	the time period during which military and civilian agencies are prepared for an enemy air attack

alert (adjective)	air alert (adjective)
engaged in or accustomed to close observation
mentally perceptive and responsive
quick and energetic

alert (verb)	air alert (verb)
warn or arouse to a sense of danger or call to a state of preparedness