Which word indicates a lack of amount or quality?

The word "paucity" directly refers to a scarcity or insufficiency in terms of amount or quality. It is often used to describe situations where there is an inadequate supply of something, such as insufficient resources, limited information, or a small quantity of a particular item. This makes it the ideal choice in this context, as it specifically highlights a lack of something essential.

In contrast, the terms "obsessive," "stoic," and "mediocrity" do not convey the same idea of scarcity or insufficiency. "Obsessive" refers to a preoccupation or fixation on something, which has more to do with intensity than a lack. "Stoic" describes a person who is able to endure pain or hardship without showing their feelings or complaining, which is unrelated to quantity or quality. "Mediocrity" indicates a state of being average or moderate but does not specifically imply a lack; rather, it suggests an absence of exceptional quality.

Thus, "paucity" is the most accurate term to indicate a lack of amount or quality in the set of choices provided.