APA Dictionary of Psychology

an infection transmitted by sexual activity. More than 20 STDs have been identified, including those caused by viruses (e.g., hepatitis B, herpes, HIV) and those caused by bacteria (e.g., chlamydia, gonorrhea, syphilis). STDs are also known as venereal diseases, the term used traditionally for syphilis and gonorrhea. Also called sexually transmitted infection (STI).