bob vs bow down

bob is a noun but bow down is not a noun.

Word	Noun	Adjective	Verb	Adverb
bob	Yes	No	Yes	No
bow down	No	No	Yes	No

bob (noun)	bow down (noun)
a short abrupt inclination (as of the head)
a short or shortened tail of certain animals
a small float usually made of cork; attached to a fishing line
a hanging weight, especially a metal ball on a string
a long racing sled (for 2 or more people) with a steering mechanism
a hair style for women and children; a short haircut all around
a former monetary unit in Great Britain

bob (verb)	bow down (verb)
cut hair in the style of a bob	bend one's knee or body, or lower one's head
make a curtsy; usually done only by girls and women; as a sign of respect	get into a prostrate position, as in submission
remove or shorten the tail of an animal
move up and down repeatedly in a quick, short movement
ride a bobsled