testis

The testis (plural: testes) is an organ in the male reproductive system. In everyday speech, people often say "testicle." This oval-shaped gland makes sperm, the cells that can fertilize an egg, and it also produces testosterone, the main male sex hormone. It sits in the scrotum, a sac outside the body, because sperm are made best at a temperature slightly lower than normal body temperature. In simple terms, this is where sperm production and much of male hormone production begin.

The testis is one of two oval-shaped organs found in the scrotum. While people often say "testicle" in everyday conversation, testis is the formal anatomical term. These organs are central to male reproduction because they produce sperm and also make important hormones.

Inside the testis, sperm develop through a process called spermatogenesis. At the same time, specialized cells produce testosterone, a hormone that affects sexual development, sex drive, muscle mass, bone strength, and mood. The scrotum is outside the body because sperm production works better at a temperature slightly lower than normal body temperature.

The word comes from Latin, and in medical writing the plural form is testes. Problems affecting the testes can change fertility, hormone levels, and general health. For example, injury, infection, twisting of the organ, or cancer can all interfere with their normal function.

In medical contexts, you might hear terms like orchitis (inflammation of a testis), testicular torsion, or testicular cancer. Although it is a sensitive topic for some people, understanding what this organ does helps make sense of male fertility, sexual development, and hormone health.