Less-than sign

The less-than sign is a mathematical symbol that denotes an inequality between two values. The widely adopted form of two equal-length strokes connecting in an acute angle at the left, <, 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 ​1⁄2 < 1 and −2 < 0. Since the development of computer programming languages, the less-than sign and the greater-than sign have been repurposed for a range of uses and operations.

For the use of the "<" sign as punctuation, see Bracket § Angle brackets.
<
Less-than sign
In UnicodeU+003C < LESS-THAN SIGN (HTML &#60;)
Related
See alsoU+2264 ≤ LESS-THAN OR EQUAL TO

U+2A7D ⩽ LESS-THAN OR SLANTED EQUAL TO used e. g. in Poland

U+226E ≮ NOT LESS-THAN
U+226A ≪ MUCH LESS-THAN
Different from
Different fromU+2329 〈 LEFT-POINTING ANGLE BRACKET

Computing

The less-than sign, < is an original ASCII character (hex 3C, decimal 60).

The less-than sign may be used for an approximation of the opening angle bracket, ⟨. ASCII does not have angle brackets but are standard in Unicode (U+2329 〈 LEFT-POINTING ANGLE BRACKET (HTML &#9001; · &lang;)). The latter is expected in formal texts.

Programming language

In BASIC, Lisp-family languages, and C-family languages (including Java and C++), operator < means "less than".

In Coldfusion, operator .lt. means "less than".

In Fortran, operator .LT. means "less than"; later versions allow <.

In Bourne shell, operator -lt means "less than".

Double less-than sign

The double less-than sign, <<, may be used for an approximation of the much-less-than sign, ≪ or of the opening guillemet, «. ASCII does not have a much-less-than sign.

In Bash, Perl, and Ruby, operator <<EOF (where "EOF" is an arbitrary string, but commonly "EOF" denoting "end of file") is used to denote the beginning of a here document.

In C and C++, operator << represents a binary left shift.

In the C++ Standard Library, operator <<, when applied on an output stream, acts as insertion operator and performs an output operation on the stream.

In Ruby, operator << acts as append operator when used between an array and the value to be appended.

In XPath the << operator returns true if the left operand precedes the right operand in document order; otherwise it returns false.[1]

Triple less-than sign

In PHP, operator <<<OUTPUT is used to denote the beginning of a heredoc statement (where OUTPUT is an arbitrary named variable.)

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

Less-than sign plus equals sign

The less-than sign plus the equals sign, <=, may be used for an approximation of the less-than-or-equal-to sign, ≤. ASCII does not have a less-than-or-equal-to sign, but Unicode defines it at code point U+2264.

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

In Prolog, =< means "less than or equal to" (as distinct from the arrow <=).

In Fortran, operator .LE. means "less than or equal to".

In Bourne shell and Windows PowerShell, the operator -le means "less than or equal to".

Less-than sign plus Hyphen-minus

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

Shell scripts

In Bourne shell (and many other shells), less-than sign is used to redirect input from a file. Less-than plus ampersand (<&) is used to redirect from a file descriptor.

Spaceship operator

Less-than sign is used in the spaceship operator.

HTML

In HTML (and SGML and XML), the less-than sign is used at the beginning of tags. The less-than sign may be included with &lt;. The less-than-or-equal-to sign, ≤, may be included with &le;.

Mathematics

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

See also

References
  1. "XML Path Language (XPath) 2.0 (Second Edition)". www.w3.org. W3C. 14 December 2010. Retrieved 29 October 2019.
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