A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients.

Proto-Indo-European (PIE) is the linguistic reconstruction of the common ancestor of the Indo-European languages. PIE was the first proposed proto-language to be widely accepted by linguists. Far more work has gone into reconstructing it than any other proto-language, and it is by far the best understood of all proto-languages of its age. During the 19th century, the vast majority of linguistic work was devoted to reconstruction of Proto-Indo-European or its daughter proto-languages such as Proto-Germanic, and most of the current techniques of linguistic reconstruction in historical linguistics (e.g. the comparative method and the method of internal reconstruction) were developed as a result. These methods supply all of our knowledge concerning PIE, since there is no written record of the language.