brood vs sit down

brood is a noun but sit down is not a noun.

Word	Noun	Adjective	Verb	Adverb
brood	Yes	No	Yes	No
sit down	No	No	Yes	No

brood (noun)	sit down (noun)
the young of an animal cared for at one time

brood (verb)	sit down (verb)
sit on (eggs)	show to a seat; assign a seat for
think moodily or anxiously about something	be in a position in which one's upper body is largely upright and supported by one's backside
be in a huff; be silent or sullen	take a seat
be in a huff and display one's displeasure
hang over, as of something threatening, dark, or menacing