study vs bone up

study is a noun but bone up is not a noun.

Word	Noun	Adjective	Verb	Adverb
study	Yes	No	Yes	No
bone up	No	No	Yes	No

As verbs, bone up is a hyponym of study; that is, bone up is a word with a more specific, narrower meaning than study:

Other hyponyms of study include con, learn, memorise, memorize, bone, cram, drum, get up, grind away, mug up, swot, swot up.

study (noun)	bone up (noun)
a detailed critical inspection
a room used for reading and writing and studying
preliminary drawing for later elaboration
attentive consideration and meditation
a branch of knowledge
applying the mind to learning and understanding a subject (especially by reading)
a state of deep mental absorption
a written document describing the findings of some individual or group
a composition intended to develop one aspect of the performer's technique
someone who memorizes quickly and easily (as the lines for a part in a play)

study (verb)	bone up (verb)
be a student of a certain subject	study intensively, as before an exam
learn by reading books
consider in detail and subject to an analysis in order to discover essential features or meaning
be a student; follow a course of study; be enrolled at an institute of learning
think intently and at length, as for spiritual purposes
give careful consideration to