Although sometimes used in error as interchangeable terms, the words sperm and semen refer to distinctly different, yet related, objects. The primary difference between sperm and semen is that sperm are the actual sex cells, whereas semen is the fluid in which the sperm are located. Both of these are necessary for the successful reproduction of human beings.
Reference: wisegeek.com (2016) . What Is the Difference between Sperm and Semen? available from: < http://www.wisegeek.com/what-is-the-difference-between-sperm-and-semen.htm >. [11 Feb 2016].