∞
Symbol  Format  Data 

∞  Code Point  U+221E 
TeX  \infty 

SVG 
The infinity symbol in math represents the concept of infinity. Typically, the symbol is used in an expression like this:
In plain language, this expression represents the limit of the expression as the variable approaches infinity.
The limit operator describes the result of an expression as a variable approaches a value. The operator is used in calculus to formalize what mathematicians mean by approach.
A series is the sum of the terms of a sequence. It can be finite or infinite, depending on the underlying sequence. In calculus, series are used to approximate functions, study convergence and divergence, and understand the behavior of infinite sums.