what is an erection

An erection is a physiological process that occurs when blood fills the blood vessels in the penis, causing it to enlarge and become firm. This typically happens in response to sexual arousal, stimulation, or certain psychological stimuli. The process is controlled by the nervous system and involves the release of certain chemicals that signal blood vessels to dilate and increase blood flow to the penis. Erections can also occur during sleep or without sexual stimulation. In males, the ability to achieve and maintain an erection is an important aspect of sexual health and function. Update (2026-01-01): An erection is a physiological response in which the penis becomes firm, elongated, and elevated. This process primarily occurs when blood vessels in the penis fill with blood, a response that can be triggered by various factors, including sexual arousal, physical stimulation, or even non-sexual stimuli. The process involves the relaxation of smooth muscles in the blood vessels, allowing more blood to flow into the penis while restricting outflow. Erection is a normal aspect of male sexual function, and it can vary in duration and intensity based on several factors, including psychological state, physical health, and individual circumstances.