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 typical mathematical usage, the less-than sign is typically placed between the two values being compared and signals that the first number is less than the second number. Examples of typical usage include ½ < 1 and −2 < 1. 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.
The less-than sign (<) is an original ASCII character (hex 3C, decimal 60).
The less-than sign is used for an approximation of the opening angle bracket (⟨). ASCII does not have angle brackets.
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
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.
Triple less-than sign
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 (<=) is 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 Fortran, operator .LE. means "less than or equal to".
Less-than sign plus Hyphen-minus
Less-than sign is used in the spaceship operator.
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.