≜ Delta Equal To: The "Defined As" Symbol Explained
The ≜ symbol, officially known as "Delta Equal To," represents the mathematical concept of "defined as" or "equal to by definition." It combines a standard equals sign with a Greek lowercase or uppercase delta (Δ) resting on top. Mathematicians, scientists, and programmers use this symbol to establish that a variable or expression is being explicitly defined in that exact moment, rather than expressing a pre-existing equality between two separate things.
In the Unicode Standard, ≜ is located at code point U+225C and belongs to the Mathematical Operators block. This block hosts a massive collection of symbols used across logic, set theory, and calculus. Since its early introduction to Unicode, it has become the standard digital character for representing definitional equality in academic papers, technical documentation, and digital typesetting.
You will most frequently spot ≜ in higher-level math textbooks, physics equations, and computer science logic. When you see an expression like x ≜ 5, it essentially means "let x be defined as 5 for the purpose of this problem." While you won't catch it trending in social media hashtags or casual text messages, it is incredibly popular in LaTeX documents and technical programming forums like Stack Overflow, where precise definitions matter and ambiguity ruins code.
Typing the ≜ symbol requires a quick shortcut depending on your platform. On a Mac, press Control + Command + Space to open the Character Viewer and search for "delta equal to." On Windows, you can find it in the Character Map or type 225C followed by Alt + X in Microsoft Word. If you are building a website, use the HTML entity ≜, and if you are typing in LaTeX, the command \triangleq will generate it perfectly.
The ≜ symbol shares its "defined as" job with a few other characters. You might see ≡ (Identical To, U+2261), ≝ (Equal To By Definition, U+225D), or := (Colon Equals) used for the exact same purpose depending on the author's preference or the programming language. However, ≜ remains one of the most visually distinct options, making it a favorite for cleanly separating definitions from standard equations on a crowded whiteboard.