Don’t Repeat Yourself (DRY)

Don’t repeat yourself, or DRY, is a principle of software development aimed at reducing repetition of software patterns.

The concept was coined in Andy Hunt and Dave Thomas’s book The Pragmatic Programmer, in 1999.

This principle is also known as Duplication Is Evil, or DIE. Its nemesis is WET. It means write everything twice.

Documentation

See also The Pragmatic Programmer, Why DRY is the most over-rated programming principle and DRY Principle in PHP.

Related : Write Everything Twice (WET), SOLID, Centralization, KISS, Tech Island, You Are Not Going To Need It (YAGNI)