n. The act of amplifying or enlarging in dimensions; enlargement; extension.n. Specificallyn. In rhetoric, expansion for rhetorical purposes of a narrative, description, argument, or other discourse; a discourse or passage so expanded; an addition made in expanding.n. In logic, an increase in the logical depth (comprehension) of a term without any corresponding decrease of breadth (extension), as the expansion of “plane triangle” into “plane triangle having the sum of its angles equal to two right angles,” which is equivalent to it with respect to extension.n. In microscopy, increase of the visual area, as distinguished from magnification (which see).