| Symbol | Description |

| :----------------: | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |

| `$` | Matches the end position of the input string. |

| `(`,`)` | Marks the start and end of a subexpression. Subexpressions can be obtained for later use. |

| `*` | Matches the previous subexpression zero or more times. |

| `+` | Matches the previous subexpression one or more times. |

| `.` | Matches any single character except the newline character `\n`. |

| `[` | Marks the beginning of a bracket expression. |

| `?` | Matches the previous subexpression zero or one time, or indicates a non-greedy qualifier. |

| `\` | Marks the next character as either a special character, or a literal character, or a backward reference, or an octal escape character. For example, `n` Matches the character `n`. `\n` matches newline characters. The sequence `\\` Matches the `'\'` character, while `\(` matches the `'('` character. |

| `^` | Matches the beginning of the input string, unless it is used in a square bracket expression, at which point it indicates that the set of characters is not accepted. |

| `{` | Marks the beginning of a qualifier expression. |

| `\|` | Indicates a choice between the two. |

| Symbol | Description |

| :-------: | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |

| `*` | matches the previous subexpression zero or more times. For example, `foo*` matches `fo` and `foooo`. `*` is equivalent to `{0,}`. |

| `+` | matches the previous subexpression one or more times. For example, `foo+` matches `foo` and `foooo` but does not match `fo`. `+` is equivalent to `{1,}`. |

| `?` | matches the previous subexpression zero or one time. For example, `Your(s)?` can match `Your` in `Your` or `Yours`. `?` is equivalent to `{0,1}`. |

| `{n}` | `n` is a non-negative integer. Matches the determined `n` times. For example, `o{2}` cannot match `o` in `for`, but can match two `o` in `foo`. |

| `{n,}` | `n` is a non-negative integer. Match at least `n` times. For example, `o{2,}` cannot match `o` in `for`, but matches all `o` in `foooooo`. `o{1,}` is equivalent to `o+`. `o{0,}` is equivalent to `o*`. |

| `{n,m}` | `m` and `n` are non-negative integers, where `n` is less than or equal to `m`. Matches at least `n` times and matches up to `m` times. For example, `o{1,3}` will match the first three `o` in `foooooo`. `o{0,1}` is equivalent to `o?`. Note that there can be no spaces between the comma and the two numbers. |