Sperm: A sperm is the male "gamete" or sex cell. It combines with the female "gamete," called an ovum, to form a zygote. The formation process is called "fertilization." (see ovum, zygote). SLIDESHOW Erectile Dysfunction (ED) Causes and Treatment See Slideshow From Men's Health Resources Blocked Hair Follicle Treatment What Is Hidradenitis Suppurativa?7 Tricks to Help Improve Your Memory Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19