What do you call a small, circumscribed elevation of the skin that contains a thin, non-purulent fluid?

The term used to describe a small, circumscribed elevation of the skin filled with a thin, non-purulent fluid is "vesicle." Vesicles typically measure less than 1 centimeter in diameter and are often seen in various dermatological conditions. They can occur in response to irritation, allergic reactions, or viral infections, such as herpes simplex.

In contrast, a blister is a more general term that can encompass larger fluid-filled elevations and may include both vesicles and larger blisters. Pustules, on the other hand, are characterized by the presence of pus, making them distinctly different from vesicles. Ulcers refer to deeper skin lesions that involve the loss of the epidermis and often part of the dermis, rather than being elevated. Thus, the specificity of the definition provided aligns perfectly with the characteristics of a vesicle.