Course in General Linguistics (Open Court Classics) by Ferdinand la Saussure

The Cours de linguistique generale, reconstructed from students' notes after Saussure's death in 1913, founded modern linguistic theory by breaking the study of language free from a merely historical and comparativist approach. Saussure's new method, now known as Structuralism, has since been applied to such diverse areas as art, architecture, folklore, literary criticism, and philosophy.