Disposable is an adjective meaning the ability of something to be disposed of or thrown away after use. Many people now use the term as a noun, i.e. "a disposable" but in reality this is still an adjective as the noun (product, nappy, etc.) is implied. Disposable income is the amount of money left over from one's salary or pay for spending, saving or whatever, after all living costs have been taken out. A disposable (also called disposable product) is a product designed for a single use after which it is recycled or is disposed as solid waste. The term often implies cheapness and short-term convenience rather than medium to long-term durability. The term is also sometimes used for products that may last several months (e.g. disposable air filters) to distinguish from similar products that last indefinitely (e.g. washable air filters). The word "disposables" is not to be confused with the word "consumables" which is widely used in the mechanical world. In welding for example, welding rods, tips, nozzles, gas, etc. are considered to be "consumables" as they only last a certain amount of time before needing to be replaced.