What is the meaning of the word relapse?

The term "relapse" refers to a return to a previous state or condition, particularly in the context of health or behavior. It most often describes a situation where someone who has made progress in recovering from an illness or addiction has reverted back to their former harmful patterns or habits. This signifies a setback in their progress, which is accurately captured by the chosen answer.

In contrast, the other options do not align with the meaning of "relapse." Prevention refers to actions taken to avoid a negative outcome, endearment pertains to expressions of affection, and progression implies moving forward or advancing, all of which are contrary to the idea of reverting to a less favorable state. Therefore, "setback" best defines "relapse" as it emphasizes the idea of encountering difficulties or obstacles after having made advances.