The Not Sign (¬): Meaning, Origin, and How to Type It
The Not Sign (¬) is a mathematical symbol primarily used in formal logic and computer science to represent negation. When placed before a statement, proposition, or variable, it reverses its truth value. Simply put, if a statement is true, adding the ¬ symbol makes it false, and vice versa.
Originally adopted into mathematical notation in the early 20th century, the ¬ symbol was popularized by logic pioneers to streamline complex proofs. Before symbols like this became the standard, mathematicians had to write out wordy text to explain their boolean algebra. The sharp, right-angle design offered a clear, unmistakable visual marker for logical negation that didn't get lost among letters and numbers.
In the Unicode standard, the Not Sign is assigned the code point U+00AC and belongs to the Latin-1 Supplement block. It was officially introduced in Unicode version 1.1 back in 1993, making it a foundational character inherited from earlier encoding systems like ISO 8859-1.
You will spot the ¬ symbol most often in academic textbooks and older codebases. In propositional logic, a formula like ¬P translates directly to "not P". While essential in theoretical computer science, modern programming languages like JavaScript, C++, or Python usually drop the ¬ in favor of the exclamation mark (!) or the tilde (~) for negation. Outside of STEM fields, the symbol rarely appears in everyday typography. However, social media users occasionally co-opt the ¬ as a makeshift nose or a corner edge in text art, taking advantage of its crisp shape to build creative Kaomoji.
Typing the Not Sign requires a quick shortcut depending on your device. On Windows, hold down the Alt key and type 0172 on your numeric keypad. Mac users have it slightly easier—just press Option + L. If you are building a website and need it in HTML, simply type ¬ to render the symbol perfectly. Mobile users on iOS and Android can usually find it by flipping to the secondary math symbol menus on their touch keyboards, though copying and pasting from the web is always a quick fallback.
The ¬ symbol shares its negation duties with a few close relatives. As mentioned, the tilde (~) and the exclamation mark (!) act as its modern programming counterparts. Visually, it closely resembles the Reversed Not Sign (⌐). While mathematically meaningless, this reversed version is famous across the internet for acting as the rims of "cool shades" in classic text emojis like (⌐■_■).