Ferdinand de Saussure was a Swiss linguist who taught at the University of Geneva from 1901-1913. He published his lectures as the influential book Course in General Linguistics in 1916. In this book, Saussure introduced key concepts of linguistics, such as the linguistic sign consisting of the signifier and signified. He argued that language is a system of signs defined by social convention and relationships within the system, rather than a naming system. Saussure's work established linguistics as a distinct scientific discipline and was highly influential in the development of 20th century linguistic theory and structuralism.