WordBoundary

WordBoundary represents a boundary between words for purposes of matching in StringExpression.

Examples

StringMatchQ["hello world", __ ~~ WordBoundary ~~ __]
(* True *)

StringCases["the cat sat", WordBoundary ~~ LetterCharacter.. ~~ WordBoundary]
(* {"the", "cat", "sat"} *)

Please visit the official Wolfram Language Reference for more details.