# ifdef

> English word · Noun

## Definitions
1. A construct in source code that allows another part of the code to run only if a specified identifier is defined in the program.

## Etymology
A keyword in various programming languages, short for if defined.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/ifdef