What condition is defined as a response characterized by swelling due to excess fluid?

The condition defined as a response characterized by swelling due to excess fluid is edema. This occurs when there is an imbalance in the body's fluid regulation, leading to an accumulation of fluid in the interstitial spaces or within body cavities. Edema can result from various factors, including inflammation, heart failure, kidney issues, or even prolonged standing.

Understanding edema is crucial because it can be a symptom of underlying health issues that require attention. For instance, localized edema might result from an injury or infection, while generalized edema might indicate systemic problems, such as heart failure or liver disease. The word itself derives from the Greek term "oidēma," which suggests swelling, thus aptly describing the condition.

The other conditions listed, such as hypertension, atrophy, and hyperplasia, pertain to different physiological processes. Hypertension refers to high blood pressure, atrophy involves the decrease in size or wasting away of an organ or tissue, and hyperplasia is characterized by an increase in the number of cells in a tissue or organ. None of these terms relate directly to the accumulation of fluid, which is the defining feature of edema.