Limits are used in calculus to describe the behavior of a function as it approaches a certain value or point. It helps determine what happens to the output of a function when the input gets closer and closer to a specific value.
Continuity refers to whether or not there are any breaks, holes, or jumps in a function.
Infinitesimal: An infinitesimal is an extremely small quantity that approaches zero but is not exactly zero. It plays an important role in calculus when dealing with limits and derivatives.