expansion
ex.pan.sion \ik-'span-ch*n\ n 1: the act or process of expanding 2: the quality or state of being expanded 3: EXPANSE 4: the increase in volume of working fluid (as steam) in an engine cylinder after cutoff or in an internal-combustion engine after explosion 5a: an expanded part 5b: something that results from an act of expanding 6: the result of carrying out an indicated operation : the expression of a function in the form of a series