The ≝ Symbol (Equal To By Definition): Meaning & Usage
The ≝ symbol, officially known as "Equal To By Definition" (U+225D), is a mathematical operator used to show that one expression is deliberately defined as equal to another, rather than proven to be equal. It features a standard equals sign topped with the abbreviation "def." Mathematicians and scientists use this symbol to establish clear rules, variables, or functions at the beginning of an equation or proof.
In the vast library of digital characters, ≝ lives in the Mathematical Operators block. Its official Unicode code point is U+225D. Introduced in Unicode version 1.1 back in 1993, this character helps digital text render complex mathematical notation cleanly without needing special formatting tricks or overlapping text layers to stack the letters above the lines.
You will spot ≝ mostly in advanced mathematics, physics papers, and computer science logic. When a researcher creates a brand new variable, they use ≝ to essentially say, "I am establishing this rule right now." While it rarely appears in casual text messages, some STEM students and programmers drop it into Discord chats or Reddit threads to playfully "define" the rules of a debate or state an indisputable fact. In actual programming languages, developers typically skip this symbol and rely on the standard equals sign (=) or a colon-equals (:=) to assign values.
Typing the ≝ symbol requires a few quick keystrokes depending on your device. On a Mac, switch to the Unicode Hex Input keyboard and hold Option while typing 225D. For Windows users typing in Microsoft Word, you can simply type 225D and immediately press Alt + X to transform it into the symbol. Web developers can drop it into a webpage using the HTML entity ≝ or the hex code ≝.
The math world has several ways to express "defined as." The ≝ symbol shares its meaning with the colon equals sign (:=), which is much easier to type on a standard keyboard and heavily favored in software development. You might also encounter the Delta Equal To symbol (≜) or the Identical To symbol (≡), both of which can signify a definition depending on the specific field of study. However, ≝ remains the most literal and unambiguous choice for setting up equations.