The Mathematical Symbol "Up Tack (⊥)"

The ⊥ Symbol in Mathematics: Denoting Perpendicularity

In the vast lexicon of mathematical symbols, the ⊥ symbol, known as the "Up Tack" or "Perpendicular", has a specific and crucial role. Predominantly used in geometry and vector algebra, it signifies perpendicularity between lines, planes, or vectors.


The ⊥ symbol is employed to express that two entities (such as lines or vectors) are perpendicular to each other, meaning they meet or intersect at a right angle (90 degrees).


  • Example 1: In the context of geometry, consider two lines \( l \) and \( m \). If these lines are perpendicular, it's denoted as:
    \( l ⊥ m \)
    This signifies that the angle between lines \( l \) and \( m \) is 90 degrees.
  • Example 2: In vector algebra, if two vectors \( \mathbf{a} \) and \( \mathbf{b} \) are perpendicular, their dot product is zero. This relationship can be represented as:
    \( \mathbf{a} \cdot \mathbf{b} = 0 \) if \( \mathbf{a} ⊥ \mathbf{b} \).

To conclude, the ⊥ symbol serves as an essential notation in mathematics, particularly when detailing relationships involving right angles and orthogonality. Its presence helps mathematicians convey complex geometric and algebraic relationships with precision and clarity.

Mathematical symbol 'Up Tack'

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Codes for the ⊥ Symbol

The Symbol
Alt CodeAlt 8869
HTML Code⊥
HTML Entity⊥
CSS Code\22A5
Hex Code⊥

How To Insert the ⊥ Symbol

(Method 1) Copy and paste the symbol.

The easiest way to get the ⊥ symbol is to copy and paste it into your document.

Bear in mind that this is a UTF-8 encoded character. It must be encoded as UTF-8 at all stages (copying, replacing, editing, pasting), otherwise it will render as random characters or the dreaded �.

(Method 2) Use the "Alt Code."

If you have a keyboard with a numeric pad, you can use this method. Simply hold down the Alt key and type 8869. When you lift the Alt key, the symbol appears. ("Num Lock" must be on.)

(Method 3) Use the HTML Decimal Code (for webpages).

HTML TextOutput
<b>My symbol: &#8869;</b>My symbol: ⊥

(Method 4) Use the HTML Entity Code (for webpages).

HTML TextOutput
<b>My symbol: &perp;</b>My symbol: ⊥

(Method 5) Use the CSS Code (for webpages).

CSS and HTML TextOutput
span:after {
content: "\22A5";}
<span>My symbol:</span>
My symbol: ⊥

(Method 6) Use the HTML Hex Code (for webpages and HTML canvas).

HTML TextOutput
<b>My symbol: &#x22A5;</b>My symbol: ⊥
On the assumption that you already have your canvas and the context set up, use the Hex code in the format 0x22A5 to place the ⊥ symbol on your canvas. For example:
JavaScript Text
const x = "0x"+"E9"
ctx.fillText(String.fromCodePoint(x), 5, 5);

(Method 7) Use the Unicode (for various, e.g. Microsoft Office, JavaScript, Perl).

The Unicode for ⊥ is U+22A5. The important part is the hexadecimal number after the U+, which is used in various formats. For example, in Microsoft Office applications (e.g. Word, PowerPoint), do the following:
[Hold down Alt]
[Press x]

(The 22A5 turns into ⊥. Note that you can omit any leading zeros.)
In JavaScript, the syntax is \uXXXX. So, our example would be \u22A5. (Note that the format is 4 hexadecimal characters.)
JavaScript TextOutput
let str = "\u22A5"
document.write("My symbol: " + str)
My symbol: ⊥