 ##  [Regular Expression](/index.php/regular-expression) 

  ##  [Regular Expression](https://natural.quantumdictionary.io/regular-expression-0) 

  
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**Natural &amp; Formal Sciences Dictionary**

 
Definition

An algebraic notation for describing regular languages using operators such as concatenation, alternation (union), and Kleene star that denotes repetition; equivalent in expressive power to finite automata and regular grammars in formal language theory.