contrast

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To set in opposition in order to show or emphasize differences.
• intransitive verb To show differences when compared.
• intransitive verb Linguistics To evince a difference that can distinguish meaning.
• noun The act of contrasting; a setting off of dissimilar entities or objects.
• noun The state of being contrasted.
• noun A difference, especially a strong dissimilarity, between entities or objects compared.
• noun One thing that is strikingly dissimilar to another.
• noun The use of opposing elements, such as colors, forms, or lines, in proximity to produce an intensified effect in a work of art.
• noun The difference in brightness between the light and dark areas of a picture, such as a photograph or video image.
• noun Linguistics A difference between units, especially one that distinguishes meaning.

from The Century Dictionary.

• noun In psychological optics, the reciprocal induction of colors and brightnesses in the present field of regard.
• noun In psychology, generally, any supposed intensification or throwing into relief by juxtaposition with an opposite.
• To set in opposition, as two or more objects of a like kind, with a view to show their differences; compare by observing differences of character or qualities: used absolutely or followed by with: as, to contrast two pictures or statues; to contrast the style of Dickens with that of Thackeray.
• In the fine arts, to exhibit the differences or dissimilitude of; heighten the effect of, or show to advantage, by opposition of position, attitude, form, or color.
• To stand in contrast or opposition; exhibit diversity on comparison.
• noun Opposition; dispute.
• noun Opposition in respect of certain qualities; antagonistic difference; direct opposition: as, the contrasts and resemblances of the seasons.
• noun Comparison by exhibiting the dissimilitude or the contrariety of qualities in the things compared; the placing of opposites together in order to make the antagonism of their qualities more apparent.
• noun In the fine arts, opposition of varied forms or colors, which by juxtaposition magnify the effect of one another's peculiarities.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To set in opposition, or over against, in order to show the differences between, or the comparative excellences and defects of; to compare by difference or contrariety of qualities.
• transitive verb (Fine Arts) To give greater effect to, as to a figure or other object, by putting it in some relation of opposition to another figure or object.
• intransitive verb To stand in opposition; to exhibit difference, unlikeness, or opposition of qualities.
• noun The act of contrasting, or the state of being contrasted; comparison by contrariety of qualities.
• noun Opposition or dissimilitude of things or qualities; unlikeness, esp. as shown by juxtaposition or comparison.
• noun (Fine Arts) The opposition of varied forms, colors, etc., which by such juxtaposition more vividly express each other's peculiarities.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun countable A difference in lightness, brightness and/or hue between two colours that makes them more or less distinguishable.
• noun uncountable The degree of this difference.
• noun countable A difference between two objects, people or concepts.
• noun countable A control on a television, etc, that adjusts the amount of contrast in the images being displayed.
• noun countable, uncountable, rhetoric Antithesis.
• verb transitive To set in opposition in order to show the difference or differences between.
• verb intransitive To form a contrast.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the range of optical density and tone on a photographic negative or print (or the extent to which adjacent areas on a television screen differ in brightness)
• verb put in opposition to show or emphasize differences
• noun the opposition or dissimilarity of things that are compared
• noun the act of distinguishing by comparing differences
• verb to show differences when compared; be different
• noun the perceptual effect of the juxtaposition of very different colors
• noun a conceptual separation or distinction