Modern linguistics emerged in the late 19th century with a shift from studying language changes over time to viewing each language as a structured system at a particular point in time. This formed the basis for structuralist linguistics. Key figures included Ferdinand de Saussure, who saw language as a system of arbitrary signs, and Henry Sweet and Baudouin de Courtenay, who focused on phonetics and phonology. In the 1920s, the Prague School was established with linguists like Trubetzkoy who developed phonological theory and placed emphasis on the phoneme, and Mathesius, Danes, and Firbas who studied the relationship between word order and discourse.