Mathematical analysis
A foundational concept in mathematical analysis is the concept of limit. Limits are used to see what happens very close to things. Limits can also be used to see what happens when things get very big. For example,  is never zero, but as  gets bigger,  gets closer and closer to zero. The limit of  as  gets bigger is exactly zero. This is described by "The limit of  as  goes to infinity is zero", and written as .