Which condition is characterized by excessive hair growth?

Hypertrichosis is indeed characterized by excessive hair growth and can occur anywhere on the body, affecting both men and women. This condition can manifest as abnormal hair growth patterns, often in areas where hair is not typically found or to a degree that is more than what is considered normal for a person's age, gender, or ethnic background. It can be congenital or acquired, with various causes, including hormonal imbalances or certain medications.

Hirsutism, while also related to excessive hair growth, specifically refers to male-pattern hair growth in women. It is typically associated with hormonal issues and can result from conditions like polycystic ovary syndrome (PCOS). Therefore, while hirsutism is a form of excess hair growth, it is not as broadly defined as hypertrichosis.

Alopecia denotes hair loss, and vellus growth refers to fine, short, and light-colored hair that is usually present on the human body, which does not qualify as excessive. Thus, hypertrichosis captures the essence of excessive hair growth accurately, making it the correct choice in this case.