Definition from Wiktionary, the free dictionary
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- Rhymes: -ɑːst
- (countable) A difference in lightness, brightness and/or hue between two colours that makes them more or less distinguishable.
- (uncountable) The degree of this difference.
- The red and the orange don't have much contrast between them — I can hardly tell them apart.
- (countable) A difference between two objects, people or concepts.
- Israel is a country of many contrasts.
- (countable) A control on a television, etc, that adjusts the amount of contrast in the images being displayed.
- (countable, uncountable, rhetoric) Antithesis.
difference that makes colours more or less distinguishable
degree of this difference
difference between two objects, people or concepts
control on a television, etc
- (transitive) To set in opposition in order to show the difference or differences between.
- (intransitive) To form a contrast.
- Foreground and background strongly contrast.
- The joints which divide the sandstone contrast finely with the divisional planes which separate the basalt into pillars.
Derived terms 
set in opposition in order to show the difference or differences between