WordStem

WordStem["word"] gives a stemmed form of word, removing plurals, inflections, etc.

Examples

Stem a word:

WordStem["running"]
(* "run" *)

Stem plural forms:

WordStem["cats"]
(* "cat" *)

Apply to multiple words:

WordStem /@ {"playing", "played", "plays"}
(* {"play", "play", "play"} *)

Please visit the official Wolfram Language Reference for more details.