Pre-ejaculate (also known as pre-ejaculatory fluid, pre-seminal fluid or Cowper's fluid, and colloquially as pre-cum) is a clear, colorless, viscous fluid that is emitted from the urethra of the penis during sexual arousal and in general during sexual activity. It is similar in composition to semen but has distinct chemical differences. The presence of sperm in the fluid varies from low to absent. Pre-ejaculate functions as a lubricant and an acid neutralizer.