study vs major

study and major both are nouns.

Word	Noun	Adjective	Verb	Adverb
study	Yes	No	Yes	No
major	Yes	Yes	Yes	No

As nouns, major is a hyponym of study; that is, major is a word with a more specific, narrower meaning than study:

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

study: be a student; follow a course of study; be enrolled at an institute of learning
major: have as one's principal field of study

Other hyponyms of study include minor.

study (noun)	major (noun)
a detailed critical inspection	the principal field of study of a student at a university
a room used for reading and writing and studying	a commissioned military officer in the United States Army or Air Force or Marines; below lieutenant colonel and above captain
preliminary drawing for later elaboration	a university student who is studying a particular field as the principal subject
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 (adjective)	major (adjective)
	greater in number or size or amount
	greater in scope or effect
	of full legal age
	(of a scale or mode) having half steps between the third and fourth degrees and the seventh and eighth degrees
	of the field of academic study in which one concentrates or specializes
	of greater importance or stature or rank
	of greater seriousness or danger
	of the elder of two boys with the same family name

study (verb)	major (verb)
be a student of a certain subject	have as one's principal field of study
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