Design patterns·The named ways it goes wrong
there is a 3 in the middle of the expression and nobody left a note saying which three that is.
Magic number
Also calledmagic constant, unexplained literal
An unnamed literal embedded in code, carrying meaning that only exists in the author's head. The cost is not readability alone: the same value appearing in two places cannot be told from a coincidence, so changing one is a guess. Naming it is the smallest refactoring in this corpus and among the highest-return.