Deterioration is the process of becoming worse or breaking down over time. When something deteriorates, its condition, quality, or strength gradually declines. An abandoned house shows signs of deterioration: the paint peels, the roof leaks, and the floorboards rot. A friendship can experience deterioration when two people stop talking and drift apart.

The word emphasizes a gradual decline rather than sudden destruction. A bicycle left outside all winter undergoes deterioration as rust spreads across its chain and frame. A person's health might show deterioration if they stop exercising and eating well. A neighborhood experiences deterioration when buildings aren't maintained and services decline.

Deterioration happens when things aren't properly cared for or when natural forces like weather, age, or use take their toll. The deterioration of a hiking trail occurs when erosion washes away the path. Historic documents require special storage to prevent deterioration.

People can slow or prevent deterioration through maintenance and care. Regular oil changes can help prevent engine deterioration. Studying throughout the semester can help prevent the deterioration of your understanding of math concepts. Once deterioration begins, it can accelerate unless someone intervenes to repair the damage and restore what's been lost.