No symbol

The no symbol (also known as a prohibition sign, no sign, circle-backslash symbol, nay, interdictory circle, or universal no) is a circle with a diagonal line through it (running from top left to bottom right), surrounding a pictogram used to indicate something is not permitted. The no symbol is generally colored red, but is sometimes another color, typically black.

The Unicode code point for the prohibition sign (also called the no symbol) is U+20E0;, Combining Enclosing Circle Backslash (   ⃠   ). It is a combining character, which means that it appears on top of the character before it, so putting d⃠ will show   d⃠.   (Note: This will appear only if the character exists in an available font.) It also appears in the Webdings and Wingdings 2 fonts.

There is also a prohibition sign emoji located at U+1F6AB NO ENTRY SIGN (🚫), which does not combine with anything.

According to the ISO standard (and also under a UK Statutory Instrument), the red area must take up at least 35% of the total area of the sign within the outer circumference of the "prohibition sign". So 35% of everything within the outer edge of the "no symbol" must be the symbol itself. Additionally, for printed signs under the UK rules, the width of a "no symbol" is set at 80% the height of the area it is printed to.