alert vs brisk

alert is a noun but brisk is not a noun.

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

As adjectives, alert and brisk are synonyms defined as:

Other synonyms of alert include lively, merry, rattling, snappy, spanking, zippy.

alert (noun)	brisk (noun)
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

alert (adjective)	brisk (adjective)
engaged in or accustomed to close observation	very active
mentally perceptive and responsive	quick and energetic
quick and energetic	imparting vitality and energy

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