What term would be used to describe something that is ruinous?

The term "perniciosus" is derived from Latin and is used to describe something that is ruinous, destructive, or harmful. This adjective captures the idea of causing great harm or destruction, often implying a sense of danger or peril associated with the subject it describes.

In contrast, the other options have different meanings that do not relate to the idea of ruin or destruction. For example, "studeo" means to be eager or to study, which does not convey any notion of harm. "Dissolutus" refers to something that is loose or dissolute, often in a moral or social context, but it lacks the specific implication of ruin. Lastly, "clemens" translates to merciful or gentle, which again does not fit with the concept of being ruinous. Thus, "perniciosus" is specifically suited to describe something that brings about ruin or destruction.