A regular language is said to be star-free if it can be described by a regular expression constructed from the letters of the alphabet, the empty set symbol, all boolean operators – including complementation – and concatenation but no Kleene star.
In the context of formal languages, a regular language is classified as star-free when it can be expressed using a regular expression that consists of alphabet letters, the empty set symbol, boolean operators like complementation, and concatenation but does not include the Kleene star operator.