Ellipsis is a form of syntactic reduction that is pervasive in both written and oral communication. It has been widely studied from different perspectives, and therefore its definition has always been quite problematic. The present work attempts to define this phenomenon in the English language. An account of the different types of ellipsis is provided, by drawing a classification with examples for each category, and three main approaches for its interpretation are outlined, i.e., text linguistics, psycholinguistics, and pragmatics. The final chapter investigates the use of the different types of ellipsis in English written and spoken texts, e.g., novels, film scripts, research articles, excerpts from diaries, recipes, newspaper headlines, advertisements, transcriptions of face-to-face conversation, etc., within the frame of textual linguistics, in order to shed some light on the different functions it may perform across genres and text types.