science vs field of study

science and field of study both are nouns.

Word	Noun	Adjective	Verb	Adverb
science	Yes	No	No	No
field of study	Yes	No	No	No

As nouns, field of study is a hypernym of science; that is, field of study is a word with a broader meaning than science:

Other hypernyms of science include bailiwick, discipline, field, study, subject, subject area, subject field.

science (noun)	field of study (noun)
a particular branch of scientific knowledge	a branch of knowledge
ability to produce solutions in some problem domain