Both Uses

contrast
in
Mrs. Warren's Profession
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The dramatic reason for making the clergyman what Mrs Warren calls "an old stick-in-the-mud," whose son, in spite of much capacity and charm, is a cynically worthless member of society, is to set up a mordant contrast between him and the woman of infamous profession, with her well brought-up, straightforward, hardworking daughter.†
Act Auth *

contrast = notable difference
The critics who have missed the contrast have doubtless observed often enough that many clergymen are in the Church through no genuine calling, but simply because, in circles which can command preferment, it is the refuge of "the fool of the family"; and that clergymen's sons are often conspicuous reactionists against the restraints imposed on them in childhood by their father's profession.†
Act Auth

Definitions:

(1) (contrast as in: contrast their writing styles)
point to differences between; or compare to show differences
(2) (contrast as in: there is a contrast)
a difference -- especially a notable difference; or the side-x-side arrangement of things that draws attention to an unmissable difference
(3) (contrast as in: sharpen the picture contrast)
the difference between tones of an image -- as in a photo or video -- such as the quality of brightness or the intensity of shades or colors
(4) (meaning too rare to warrant focus)