| Syntax | Meaning | Example | Matches | DFA |
|---|---|---|---|---|
| Accepts empty string |  |
|||
| a | Matches the specified character | k | k |  |
| * | Matches 0 or more occurrence of the previous char | a* | "",a,aa,aaa,... |  |
| ? | Matches 0 or 1 occurrence of the previous char | a? | "", a |  |
| . | Matches any character occurence | a? | "", a |  |