an expanded, dilated, or enlarged portion or form of a thing: The present article is an expansion of one he wrote last year.
5.
anything spread out; expanse.
6.
Mathematics.
a.
the development at length of an expression indicated in a contracted form, as a^{2} + 2 ab + b^{2} for the expression (a + b ) ^{2} .
b.
any mathematical series that converges to a function for specified values in the domain of the function, as 1 + x + x^{2} + … for 1/(1 − x ) when x < 1.
7.
Machinery. that part of the operation of an engine in which the volume of the working medium increases and its pressure decreases.
8.
an increase in economic and industrial activity (opposed to contraction ).
1610s, "anything spread out;" 1640s, "act of expanding," from Fr. expansion, L.L. expansionem (nom. expansio) "a spreading out," from L. expandere (see expand).
An increase in the volume of a substance while its mass remains the same. Expansion is usually due to heating. When substances are heated, the molecular bonds between their particles are weakened, and the particles move faster, causing the substance to expand.
A number or other mathematical expression written in an extended form. For example, a^{2} + 2ab + b^{2} is the expansion of (a + b)^{2}.