Up Tack ⊥

The Up Tack character (⊥) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference ⊥, the decimal numeric character reference ⊥, or the hexadecimal numeric reference ⊥. The character is assigned Unicode code point U+22A5 in the Universal Character Set.

The up tack (⊥), also called the perpendicular symbol or bottom element, has multiple meanings in mathematics. It denotes perpendicularity in geometry (a ⊥ b), the bottom type in type theory, falsity in logic, and independence in probability theory.

Symbol entities encompass a wide variety of special characters used in legal disclaimers, intellectual property notices, typographic ornaments, card suit indicators, and miscellaneous notation throughout web content. These characters appear in website footers for copyright notices, product pages for trademark symbols, academic papers for dagger footnote markers, and decorative or gaming contexts for card suits and stars.

When deciding how to encode the Up Tack character in your HTML documents, the named entity ⊥ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form ⊥ and hexadecimal form ⊥ are equally valid alternatives that work in contexts where named entities may not be supported, or when generating HTML output programmatically from server-side code. All three representations produce identical visual output in every modern web browser.

Use the perpendicular symbol in geometry (lines a ⊥ b are perpendicular), logic (⊥ represents falsity), probability (independence), and type theory (bottom type). Its meaning varies by field, so context should make the intended interpretation clear.