What is "style" in Art History? How does it differ from "subject matter?"?

Works by various artists that share sufficient elements in a recognizable way. Yes, I cheated to get that answer. Examples of styles would be realism, abstractism, or cubism. Kadinsky's and Picasso's styles of painting were completely different, but shared enough philosophy for lack of a better word to be grouped as abstracts. Both artists concentrated on form, color, and line rather than a realistic or even stylized representation.

A person is a subject, as is a flower. The thing or idea is the subject matter. Styles vary a lot, from pure realism to abstract expressionism.

Style involves how something is made, where subject matter is what is represented.

Style is the different stroked and patterns the artist uses in all of his/her drawings. Subject matter is what the Art piece represents.