No symbol
The general prohibition sign, also known informally as the no symbol, 'do not' sign, circle-backslash symbol, nay, interdictory circle, prohibited symbol, is a red circle with a 45-degree diagonal line inside the circle from upper-left to lower-right. It is typically overlaid on a pictogram to warn that an activity is not permitted, or has accompanying text to describe what is prohibited. It is a mechanism in graphical form to assert 'drawn norms', i.e. to qualify behaviour without the use of words.
Appearance
According to the ISO standard, the red area must take up at least 35 percent of the total area of the sign within the outer circumference of the "prohibition sign". Under the UK rules the width of a "no symbol" is 80 percent the height of the printed area.For computer display and printing, the symbol is supported in Unicode by combining elements rather than with individual code points.
Uses
Traffic
Motor traffic
The "prohibition" symbol is used on traffic signs, so that drivers can interpret traffic laws quickly while driving. For example:- No left turn or No right turn
- No U-turn
- No parking or No estacionarse
- Road closed to vehicles, Road closed to vehicles
Non-motor traffic
- ,, No horse-riding
- ,, No bicycles
- ,, No pedestrians
- ,, No animal-drawn vehicles
General prohibitions and warnings
- No smoking.
- or No littering
- No swimming
Packaging and products
- Breakable; do not drop
- Keep away from magnetic fields
It is also used on clothing, linens, and other household products to indicate the care, treatment or cleaning of the item. For example:
- Do not iron
Promotional and advertising
Other uses
It can also be used as a symbol of opposition, to strike out the unwanted item, as in "no airport here!" with a No symbol superimposed on an aeroplane symbol.International standards
The official prohibition sign design characteristics are governed by regional and international standards. The symbol's canonical definition comes from the International Organization for Standardization which published ISO 3864-1 in 2002, a revision of a standard first published in 1984. The current version was published in 2011.ISO 3864-1 sets the rules for the color, shape, and dimensions of safety signage. The regulations include the incorporation of text and pictograms, with reference to materials used, sign size, and viewing conditions. The introduction includes language on the need for using as few words as possible to convey information.
Design specifics
The 3864 standard defines the color and design for the prohibition symbol. The verbal definition reads "circle with diagonal bar" with a red safety color, a white contrast color, and black for the graphical symbol.Dimensions per 3864-1
The symbol is defined as a circle, with the circular band having a thickness of 10% of the outer diameter of the circle. The inner diagonal line has a thickness of 8% of the outer diameter of the circle. The diagonal is centered in the circle and at a 45-degree angle going from upper left to lower right. It is recommended to have a white outside border that is 2.5% to 5% of the outer diameter of the circle.The circle and line are red, the background is white, and the pictogram or descriptive text is black.
Color red per 3864-1
The standard defines the range of CIE x,y chromacity coordinates for the color red to be used, relative to the CIE 1931 2° standard observer. They also list equivalent colors for various common color systems such as Munsell, defining red as Munsell 7,5R 4/14.Relative to CSS colors for the web and sRGB, and assuming a white background of
#ffffff, the red color should be no lighter than #f80000, and no darker than #a00000, with #b00000 being a useful choice in terms of good contrast and color.Variations
Non-conforming designs
Despite the fact that the ISO standard is freely available, it is not uncommon for graphic artists to improvise on the particular color and dimensions. As a result, there is a wide variation of the symbol in common use, for instance using a lower-contrast red than specified in the standard or using the same width for the diagonal line as the circle.For example, compare with .
Alternate or regional design differences
Circles with red borders and no slanted or diagonal line are used under the Vienna Convention on Road Signs and Signals to indicate "No entry to vehicles with the following characteristics" such as height, width, mass, or speed. The European Vienna Convention prohibits a diagonal line in the symbol for any sign other than no turning signs. An alternative use for red bordered circles is as a Mandatory Action Symbol type B.In many jurisdictions, 'no entry' is indicated by a solid red disc with white horizontal bar. See the general article on Prohibitory traffic signs.
A blue filled circle with an illustration or legend means that a lane is restricted to a particular class of users as shown, and no other traffic may use it. In contrast, a blue filled circle without a diagonal line through it is used as a Mandatory Action Symbol, indicating that the activity represented inside the circle is mandatory and must be executed.
Unicode and fonts
Unicode character
The Unicode code point for the prohibition sign is.Unicode combining character
There is also, which also represents prohibition. It is a combining character, which means that it appears on top of the character immediately before it.Example: Putting
W⃠ in html will display the letter W inside the prohibition sign: W⃠.Emoji and other unicode versions
There are also several prohibition sign emojis and related unicode characters:In fonts
Similar-appearing symbols
There are Unicode code points for other glyphs that look very similar to the 'prohibited' symbol, but which may be available in more font repertoires:- , which is difficult to distinguish from the 'prohibited' symbol.