guard vs baby-sit

guard is a noun but baby-sit is not a noun.

Word	Noun	Adjective	Verb	Adverb
guard	Yes	No	Yes	No
baby-sit	No	No	Yes	No

As verbs, baby-sit is a hyponym of guard; that is, baby-sit is a word with a more specific, narrower meaning than guard:

Other hyponyms of guard include patrol, police, keep guard, stand guard, stand sentinel, stand watch, babysit, sit, babysit.

guard (noun)	baby-sit (noun)
a position on a basketball team
the duty of serving as a sentry
(American football) a position on the line of scrimmage between the center and the tackles
a precautionary measure warding off impending danger or damage or injury etc.
a device designed to prevent injury or accidents
a posture of defence in boxing or fencing
a military unit serving to protect some place or person
the person who lines up between the center and the tackles on the offensive line of a football team on the line of scrimmage
a person who keeps watch over something or someone
the person who plays the position of guard on a basketball team

guard (verb)	baby-sit (verb)
watch over or shield from danger or harm; protect	work or act as a baby-sitter
protect against a challenge or attack	take watchful responsibility for
to keep watch over
take precautions in order to avoid some unwanted consequence