Ferdinand de Saussure was a Swiss linguist and semiotician whose ideas laid a foundation for many significant developments in both linguistics and semiology in the 20th century. He is widely considered one of the founders of modern linguistics and his work established the structuralist approach to language. His most influential work, Course in General Linguistics, was published posthumously by his students and introduced the concept of the linguistic sign as being composed of a signifier and a signified. Saussure's distinction between langue (the abstract language system) and parole (individual speech acts) remains a cornerstone of linguistic theory.