Which condition is characterized by a male's inability to achieve or maintain an erection?

Erectile dysfunction is the term specifically used to describe a male's inability to achieve or maintain an erection sufficient for satisfactory sexual performance. This condition can be caused by a variety of factors, including psychological issues, medical conditions, and lifestyle choices. It can manifest as difficulty in achieving an erection, maintaining an erection during sexual activity, or a decrease in sexual desire.

In the context of the other options, infertility refers to a man's inability to conceive a child, which may or may not involve erectile dysfunction. Hypogonadism involves low testosterone levels, which can affect libido and sexual function, but it is not solely defined by the symptoms of erectile dysfunction. Prostatitis is an inflammation of the prostate gland that can lead to symptoms such as pain during urination or ejaculation, but it does not specifically address the ability to achieve or maintain an erection. Therefore, erectile dysfunction is the most specific and precise term for the condition described in the question.