# Triple bar

Identical to
Not identical to
Punctuation Word dividers General typography Intellectual property Currency apostrophe ( ’ ' ) brackets ( [ ], ( ), { }, ⟨ ⟩ ) colon ( : ) comma ( , ، 、 ) dash ( ‒, –, —, ― ) ellipsis ( …, ..., . . . ) exclamation mark ( ! ) full stop / period ( . ) hyphen ( ‐ ) hyphen-minus ( - ) question mark ( ? ) quotation marks ( ‘ ’, “ ”, ' ', " " ) semicolon ( ; ) slash / stroke / solidus ( /,  ⁄  ) interpunct ( · ) space ( ) ( ) ( ) ampersand ( & ) asterisk ( * ) at sign ( @ ) backslash ( \ ) bullet ( • ) caret ( ^ ) dagger ( †, ‡ ) degree ( ° ) ditto mark ( ″ ) inverted exclamation mark ( ¡ ) inverted question mark ( ¿ ) number sign / pound / hash ( # ) numero sign ( № ) obelus ( ÷ ) ordinal indicator ( º, ª ) percent, per mil ( %, ‰ ) plus and minus ( + − ) basis point ( ‱ ) pilcrow ( ¶ ) prime ( ′, ″, ‴ ) section sign ( § ) tilde ( ~ ) underscore / understrike ( _ ) vertical bar / broken bar / pipe ( ¦, | ) copyright symbol ( © ) registered trademark ( ® ) service mark ( ℠ ) sound recording copyright ( ℗ ) trademark ( ™ ) currency (generic) ( ¤ ) currency (specific) ( ) asterism ( ⁂ ) hedera ( ❧ ) index / fist ( ☞ ) interrobang ( ‽ ) irony punctuation ( ⸮ ) lozenge ( ◊ ) reference mark ( ※ ) tie ( ⁀ ) diacritical marks logic symbols whitespace characters non-English quotation style ( « », „ ” ) Chinese punctuation Hebrew punctuation Japanese punctuation Korean punctuation

The triple bar, , is a symbol with multiple, context-dependent meanings. It has the appearance of a "=" sign with a third line. The triple bar character in Unicode as codepoint U+2261 identical to (HTML: &#8801; &equiv;). LaTeX \equiv corresponds to the triple bar.

In logic, it has a similar meaning to the if and only if connective, ⇔. However, in some texts ⇔ is used as a symbol in logic formulas, while ≡ is for reasoning about those formulas (as in metalogic).

In mathematics, it is sometimes used a symbol for congruence (although not the only one). Particularly, in number theory, it has the meaning of modular congruence: $a \equiv b \pmod N$ if N divides ab.

This symbol is also used when it appears in an equation which is a definition of its left-hand side, that is an equation which is not derived but instead defined.

It is also used for "identical equality" of functions; one writes $f \equiv g$ for two functions f, g if we have $f(x) = g(x)$ for all x.

In botanical nomenclature, the triple bar denotes homotypic synonyms (those based on the same type specimen), to distinguish them from heterotypic synonyms (those based on different type specimens), which are marked with an equals sign.[1]

In chemistry, the triple bar can be used to represent a triple bond between atoms. For example, HC≡CH is a common shorthand for acetylene.

## References

1. ^ "Guidelines for authors" (PDF). Taxon 62 (1): 211–214. 2013.