Which term relates to a hospital or infirmary?

The term that relates to a hospital or infirmary is "nosocomial." This word originates from the Greek word "nosokomeion," which means "hospital." In medical terminology, nosocomial refers specifically to infections that are acquired in a hospital setting that were not present or incubating at the time of a patient's admission. Therefore, it directly connects to the context of hospitals and healthcare environments, making it the clear answer in this question.

The other options pertain to different medical terminologies that do not relate to a hospital or infirmary. For instance, "nullipara" refers to a woman who has never given birth, "nidus" typically denotes a nest or focus, often used in discussions about disease sites, and "oliguria" describes a condition of low urine output. None of these terms directly relate to the context of a hospital or infirmary like "nosocomial" does.