Alphabet used in regular expressions

A regular expression is a formal description of the structure of a word or a field value.

Regular expression syntax

Name	Symbol	Example
Any character	`*`	`"c"*"t"` allows words such as cat and cot.
Letter	`C`	`C"ot"` allows words such as Rot, pot, cot, Dot, and mot.
Uppercase letter	`A`	`A"ot"` allows words such as Rot, Cot, Mot, and Dot.
Lowercase letter	`a`	`a"ot"` allows words such as rot, cot, mot, and dot.
Letter or number	`X`	`X` allows any standalone number or letter.
Number	`N`	`N"th"` allows words such as 5th, 4th, and 6th.
String	`" "`	`"cot"`
Or	`\|`	`"pl"("o"\|"a")"t"` allows the words “plot” and “plat”.
Character from group	`[]`	`[tm]"ot"` allows the words “tot” and “mot”.
Character not from group	`[^]`	`[^t]"ot"` allows words such as “cot” and “lot”, but not the word “tot”.
Any number of repetitions (applies to the expression or subexpression on the left)	`{-}`	`[AB74]{-}` allows any combination of the characters A, B, 7, and 4, of any length.
Number of repetitions n	`{n}`	`N{2}"th"` allows words such as 25th, 84th, and 11th.
From n to m repetitions	`{n-m}`	`N{1-3}"th"` allows words such as 5th, 84th, and 111th.
From 0 to n repetitions	`{-n}`	`N{-2}"th"` allows words such as 84th and 5th.
From n repetitions and more	`{n-}`	`N{2-}"th"` allows words such as 25th, 834th, 311th, and 34576th.
Subexpression	`()`
Hyphen symbol	`[\-]`
Slash symbol	`[\\]`

Postal code – [0-9]{6} (sample value: 142172)
Zip code (USA) – [0-9]{5}("-"[0-9]{4}){-1} (sample values: 55416, 33701-4313)
Income – N{4-8}[,]N{2} (sample values: 15000,00, 4499,00)
Month in numerical form – ((|"0")[1-9])|("10")|("11")|("12") (sample values: 4, 05, 12)
Fraction – ("-"|)([0-9]{1-})(|(("."|",")([0-9]{1-}))) (sample values: 1234,567, 0.99, 100,0, -345.6788903)
Email – [A-Za-z0-9_]{1-}(("."|"-")[A-Za-z0-9_]{1-}){-3}"@"[A-Za-z0-9_]{1-}(("."|"-")[A-Za-z0-9_]{1-}){-4}"."([A-Za-z]{2-4}|"asia"|"museum"|"travel"|"example"|"localhost" (sample values: support@abbyy.com, my-name@company.org.ru, info@gallery.museum)