View source for Less-than sign

{{short description|Mathematical symbol representing the relation "less than"}}
{{More references|date=June 2019}}
{{Infobox symbol
|mark=<
|name=Less-than sign
|unicode = {{unichar|003C|Less-than sign|html=}}
|see also= {{unichar|003E|GREATER-THAN SIGN|nlink=Greater-than sign}}<br/>{{unichar|2264|Less-than or equal to}}<br />
{{Unichar|2A7D|LESS-THAN OR SLANTED EQUAL TO}} used e.g. in Poland<br />
{{unichar|226E|NOT LESS-THAN}}<br />{{unichar|226A|Much less-than}} 
|different from = {{unichar|2329|Left-POINTING ANGLE BRACKET|nlink=Bracket#Angle brackets}}
}}
The '''less-than sign''' is a mathematical symbol that denotes an [[Inequality (mathematics)|inequality]] between two values. The widely adopted form of two equal-length strokes connecting in an acute angle at the left, {{char|<}}, has been found in documents dated as far back as the 1560s. In mathematical writing, the less-than sign is typically placed between two values being compared and signifies that the first number is less than the second number. Examples of typical usage include {{math|{{frac|1|2}} < 1}} and {{math|−2 < 0}}. 

Since the development of computer programming languages, the less-than sign and the [[Greater-than sign|greater-than sign]] have been repurposed for a range of uses and operations.

==Computing==
The '''less-than sign''', {{char|<}}, is an original [[ASCII]] character (hex 3C, decimal 60).

===Programming===
In [[BASIC]], [[Lisp (programming language)|Lisp]]-family languages, and [[C (programming language)|C]]-family languages (including [[Java (programming language)|Java]] and [[C++]]), comparison operator <code>&lt;</code> means "less than".

In Coldfusion, operator <code>.lt.</code> means "less than".

In [[Fortran]], operator <code>.LT.</code> means "less than"; later versions allow <code>&lt;</code>.

====Shell scripts====
In [[Software:Bourne shell|Bourne shell]] (and many other shells), operator <code>-lt</code> means "less than". Less-than sign is used to [[Redirection (computing)|redirect]] input from a file. Less-than plus ampersand ({{code|<&}}) is used to redirect from a [[File descriptor|file descriptor]].

====Double less-than sign====
The '''double less-than sign''', {{char|<<}}, may be used for an approximation of the ''much-less-than sign'' ({{char|≪}}) or of the opening guillemet ({{char|«}}). ASCII does not encode either of these signs, though they are both included in [[Unicode]].

In [[Software:Bash (Unix shell)|Bash]], [[Perl]], and [[Ruby (programming language)|Ruby]], operator {{code|<<EOF}} (where "EOF" is an arbitrary string, but commonly "EOF" denoting "end of file") is used to denote the beginning of a [[Here document|here document]].

In [[C (programming language)|C]] and [[C++]], operator {{code|<<}} represents a [[Bitwise operation#Shifts in C, C++, C#, Python|binary left shift]].

In the [[Software:C++ Standard Library|C++ Standard Library]], operator {{code|<<}}, when applied on an output stream, acts as ''insertion operator'' and performs an output operation on the stream.

In [[Ruby (programming language)|Ruby]], operator {{code|<<}} acts as ''append operator'' when used between an array and the value to be appended.

In [[XPath]] the {{code|<<}} operator returns true if the left operand precedes the right operand in document order; otherwise it returns false.<ref>{{cite web |date=14 December 2010 |title=XML Path Language (XPath) 2.0 (Second Edition) |url=https://www.w3.org/TR/xpath20/#id-node-comparisons |archive-url=https://web.archive.org/web/20221007124416/https://www.w3.org/TR/xpath20/#id-node-comparisons |archive-date=7 October 2022 |access-date=29 October 2019 |website=www.w3.org |publisher=W3C}}</ref>

====Triple less-than sign====
In [[Organization:PHP|PHP]], operator {{code|<<<OUTPUT}} is used to denote the beginning of a [[Here document|heredoc]] statement (where <code>OUTPUT</code> is an arbitrary named variable.)

In Bash, {{code|<<<word}} is used as a "here string", where {{code|word}} is expanded and supplied to the command on its standard input, similar to a heredoc.

====Less-than sign with equals sign====
The less-than sign with the equals sign, {{code|1=<=}}, may be used for an approximation of the [[Inequality (mathematics)|less-than-or-equal-to sign]], {{char|≤}}. ASCII does not have a less-than-or-equal-to sign, but [[Unicode]] defines it at code point U+2264.

In [[BASIC]], [[Lisp (programming language)|Lisp]]-family languages, and [[C (programming language)|C]]-family languages (including [[Java (programming language)|Java]] and [[C++]]), operator {{code|1=<=}} means "less than or equal to". In [[Sinclair BASIC]] it is encoded as a single-byte code point token.

In [[Prolog]], {{code|1==<}} means "less than or equal to" (as distinct from the arrow {{code|1=<=}}).

In [[Fortran]], operators {{code|.LE.}} and {{code|1=<=}} both mean "less than or equal to".

In [[Software:Bourne shell|Bourne shell]] and Windows PowerShell, the operator {{code|-le}} means "less than or equal to".

====Less-than sign with hyphen-minus====
In the [[R (programming language)|R programming language]], the less-than sign is used in conjunction with a hyphen-minus to create an arrow ({{code|<-}}), this can be used as the left assignment operator.

====Spaceship operator====
Less-than sign is used in the spaceship operator.

====HTML====
In [[HTML]] (and [[Standard Generalized Markup Language|SGML]] and [[XML]]), the less-than sign is used at the beginning of tags. The less-than sign may be included with <code>&amp;lt;</code>. The less-than-or-equal-to sign, {{char|≤}}, may be included with <code>&amp;le;</code>.

==Unicode==
[[Unicode]] provides various Less Than Symbol:<ref>{{Cite web |title=Less than symbol |url=https://lessthansymbol.com/ |access-date=2023-06-06 |archive-date=2023-05-16 |archive-url=https://web.archive.org/web/20230516200208/https://lessthansymbol.com/ |url-status=live }}</ref>
{| class="wikitable"
! Symbol !!  Name !!  Code Point
|-
| ⍃ || Apl Functional Symbol Quad Less Than || U+2343
|-
| ⧀ || Circled Less Than || U+29C0
|-
| ⦖ || Double Right Arc Less Than Bracket || U+2996
|-
| ⋜ || Equal To Or Less Than || U+22DC
|-
| ⦓ || Left Arc Less Than Bracket || U+2993
|-
| ⥷ || Leftwards Arrow Through Less Than || U+2977
|-
| ⥶ || Less Than Above Leftwards Arrow || U+2976
|-
| ≨ || Less Than But Not Equal To || U+2268
|-
| ⋦ || Less Than But Not Equivalent To || U+22E6
|-
| ≤ || Less Than Or Equal To || U+2264
|-
| ≲ || Less Than Or Equivalent To || U+2272
|-
| ≦ || Less Than Over Equal To || U+2266
|-
| < || Less Than Sign || U+003C
|-
| ⩹ || Less Than With Circle Inside || U+2A79
|-
| ⋖ || Less Than With Dot || U+22D6
|-
| ≪ || Much Less Than || U+226A
|-
| ≰ || Neither Less Than Nor Equal To || U+2270
|-
| ≴ || Neither Less Than Nor Equivalent To || U+2274
|-
| ≮ || Not Less Than || U+226E
|-
| ⋘ || Very Much Less Than || U+22D8
|}

The less-than sign may be seen for an approximation of the opening [[Bracket#Angle brackets|angle bracket]], {{char|⟨}}. True angle bracket characters, as required in [[Notation#Linguistics|linguistics notation]], are expected in formal texts.

==Mathematics==
In an inequality, the less-than sign and greater-than sign always "point" to the smaller number. Put another way, the "jaws" (the wider section of the symbol) always direct to the larger number.

==See also==
*[[Inequality (mathematics)]]
*[[Greater-than sign]]
*[[Relational operator]]
*Much-less-than sign

==References==
{{Reflist}}

[[Category:Mathematical symbols]]
[[Category:Inequalities]]

{{Sourceattribution|Less-than sign}}