What is an STI? An STI refers to a Sexually Transmitted Infection. Many terms have been employed over the years that refer to illnesses transmitted by humans through direct sexual contact. For a long time, the term that was most in vogue was venereal disease. The word “venereal” is derived from venereus, a Latin word that refers to sexual intercourse or desire as well as to Venus, the Roman goddess of love. Then sometime in the 1990s, the term venereal disease fell out of fashion, replaced by sexually transmitted disease (STD) and, later, sexually transmitted infection (STI). If you want to learn more, visit our blog post specifically about the differences between STIs and STDs.