This book constitutes the refereed proceedings of the 4th International Workshop on Controlled Natural Language, CNL 2014, held in Galway, Ireland, in August 2014. The 17 full papers and one invited paper presented were carefully reviewed and selected from 26 submissions. The topics include simplified language, plain language, formalized language, processable language, fragments of language, phraseologies, conceptual authoring, language generation, and guided natural language interfaces.