> ## Documentation Index
> Fetch the complete documentation index at: https://docs.abbyy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Alphabet used in regular expressions

> Reference guide for regular expression syntax used in ABBYY Vantage Scanning Station.

Scanning Station uses a custom regular-expression alphabet for validating registration-parameter values. The tokens below describe the available syntax.

| Name                      | Conventional designation | Usage example                                                                 |
| :------------------------ | :----------------------- | :---------------------------------------------------------------------------- |
| Any character             | `*`                      | `` `"c"*"t"` `` allows words like `cat`, `cot`, etc.                          |
| Letter                    | `C`                      | `` `C"ot"` `` allows words like `Rot`, `pot`, `cot`, `Dot`, `mot`, etc.       |
| Uppercase letter          | `A`                      | `` `A"ot"` `` allows words like `Rot`, `Cot`, `Mot`, `Dot`, etc.              |
| Lowercase letter          | `a`                      | `` `a"ot"` `` allows words like `rot`, `cot`, `mot`, `dot`, etc.              |
| Letter or number          | `X`                      | `` `X` `` allows any standalone number or letter.                             |
| Number                    | `N`                      | `` `N"th"` `` allows words like `5th`, `4th`, `6th`, etc.                     |
| String                    | `" "`                    | `` `"cot"` ``                                                                 |
| Or                        | `\|`                     | `` `"pl"("o"\|"a")"t"` `` allows `"plot"` and `"plat"`.                       |
| Character from group      | `[]`                     | `` `[tm]"ot"` `` allows `"tot"` and `"mot"`.                                  |
| Character not from group  | `[^]`                    | `` `[^t]"ot"` `` allows `"cot"`, `"lot"`, etc., but not `"tot"`.              |
| Space (within group)      | `\s`                     | `` `[A\s]` `` allows only the letter `A` or a space.                          |
| Any number of repetitions | `{-}`                    | `` `[AB74]{-}` `` allows any combination of `A`, `B`, `7`, `4` of any length. |
| Exactly n repetitions     | `{n}`                    | `` `N{2}"th"` `` allows `25th`, `84th`, `11th`, etc.                          |
| From n to m repetitions   | `{n-m}`                  | `` `N{1-3}"th"` `` allows `5th`, `84th`, `111th`, etc.                        |
| From 0 to n repetitions   | `{-n}`                   | `` `N{-2}"th"` `` allows `84th`, `5th`, etc.                                  |
| n or more repetitions     | `{n-}`                   | `` `N{2-}"th"` `` allows `25th`, `834th`, `311th`, `34576th`, etc.            |
| Subexpression             | `()`                     | —                                                                             |
| Hyphen symbol             | `[\-]`                   | —                                                                             |
| Slash symbol              | `[\\]`                   | —                                                                             |

## Examples of regular expressions

| Purpose           | Pattern                                                                                                                                                                 | Sample values                                                        |
| :---------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------- |
| Postal code       | `[0-9]{6}`                                                                                                                                                              | `142172`                                                             |
| Zip code (USA)    | `[0-9]{5}("-"[0-9]{4}){-1}`                                                                                                                                             | `55416`, `33701-4313`                                                |
| Income            | `N{4-8}[,]N{2}`                                                                                                                                                         | `15000,00`, `4499,00`                                                |
| Month (numerical) | `((\|"0")[1-9])\|("10")\|("11")\|("12")`                                                                                                                                | `4`, `05`, `12`                                                      |
| Fraction          | `("-"\|)([0-9]{1-})(\|((".",")([0-9]{1-})))`                                                                                                                            | `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")` | `support@abbyy.com`, `my-name@company.org.ru`, `info@gallery.museum` |

## Related topics

* [Registration parameters in batches](/vantage/documentation/scanning-station/interface/registration-params-batches)
* [Registration Parameters window](/vantage/documentation/scanning-station/interface/registration-params-window)
* [Index documents manually](/vantage/documentation/scanning-station/operator/index-manually)
* [Appendix](/vantage/documentation/scanning-station/appendix/appendix)