What is the medical term for swelling or increased fluid buildup in tissue?

The term "edema" specifically refers to the accumulation of excess fluid in the interstitial spaces of tissues, leading to swelling. This condition can occur in various parts of the body and is often a result of an underlying issue such as inflammation, heart failure, or kidney problems.

By contrast, while "effusion" also pertains to fluid buildup, it typically refers to fluid accumulation in a specific cavity, such as the pleural space around the lungs or the joint space. "Inflammation" describes a broader biological response to harmful stimuli, including inflammation, redness, heat, and swelling, but it does not exclusively refer to fluid accumulation. "Puffiness" is more of a colloquial term and lacks the precise medical definition required for an accurate response. Thus, "edema" is the most appropriate medical term for the phenomenon described in the question.