alert vs merry

alert is a noun but merry is not a noun.

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

As adjectives, alert and merry are synonyms defined as:

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

alert (noun)	merry (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)	merry (adjective)
engaged in or accustomed to close observation	quick and energetic
mentally perceptive and responsive	offering fun and gaiety
quick and energetic	full of or showing high-spirited merriment

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