durability

thumb|The Manx Electric Railway on the [[Isle of Man still operates with its original tramcars and trailers, all of which are over one hundred years old, the latest dating from 1906.]]

Durability is the ability of a physical product to remain functional, without requiring excessive maintenance or repair, when faced with the challenges of normal operation over its design lifetime. There are several measures of durability in use, including years of life, hours of use, and number of operational cycles. In economics, goods with a long usable life are referred to as durable goods.