According to the Merriam-Webster Dictionary calculus is an advanced branch of mathematics that deals mostly with rates of change and with finding lengths, areas, and volumes.
The word calculus comes from the Latin word for a stone used in counting.
Topics in calculus
The subject of calculus as presented in a typical college curriculum include 
- Theory of Limits
- Sequences and Series
- Differential Calculus
- Integral Calculus
- Partial Derivatives
- Iterated (or Multidimensional) Integrals
- Merriam-Webster. (2004). Merriam-Webster's collegiate dictionary. Merriam-Webster.
- Greenspan, H. P., Benney, D. J., & Turner, J. E. (1986). Calculus: an introduction to applied mathematics. McGraw-Hill Ryerson Ltd.