Juxtaposition
Etymology
From French "juxtaposition," coined from Latin juxta, "close by, beside," and the noun of position, from ponere, "to place." It entered English in the eighteenth century as a scientific and then critical term for simple side-by-side placement. In the arts it took on the sense of a placement chosen to make one thing comment on another.
noun · /juk-stuh-puh-ZIH-shun/
The placing of two things side by side, especially to highlight a contrast or connection.
What it names
The deliberate pairing — a luxury ad beside a breadline, a tender line next to a brutal one — that makes meaning spark from the gap between two things, without a word of explanation.
Example
The exhibit’s power came from juxtaposition: a child’s drawing hung inches from the police report that ended the same day.
Related idea
Juxtaposition merely sets two things side by side; a foil is one character or element placed specifically to bring out the qualities of another by contrast.