grind vs grind down

grind is a noun but grind down is not a noun.

Word	Noun	Adjective	Verb	Adverb
grind	Yes	No	Yes	No
grind down	No	No	Yes	No

grind (noun)	grind down (noun)
the act of grinding to a powder or dust
hard monotonous routine work
the grade of particle fineness to which a substance is ground
an insignificant student who is ridiculed as being affected or boringly studious

grind (verb)	grind down (verb)
reduce to small pieces or particles by pounding or abrading	rule a country as a tyrant
make a grating or grinding sound by rubbing together
press or grind with a crushing noise
shape or form by grinding
created by grinding
dance by rotating the pelvis in an erotically suggestive way, often while in contact with one's partner such that the dancers' legs are interlaced
work hard