Pronunciation: (ik-span'shun),[key] —n. 1. the act or process of expanding.
2. the state or quality of being expanded.
3. the amount or degree of expanding.
4. 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. Math. a. the development at length of an expression indicated in a contracted form, as a2 + 2ab + b2 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 + x2 + … for 1/(1 - x) when x < 1.
7. Mach.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).