Our patron saint of linguistics for May is Ferdinand de Saussure (b. 1857, d. 1913), a Swiss linguist considered one of the fathers of modern linguistics.
As a student, Saussure studied Latin, Ancient Greek, Sanskrit, and even Celtic. In 1878, at the age of 21, he published a Dissertation on the Primitive Vowel System in Indo-European Languages. In his work on Proto Indo-European, he proposed the existence of missing phonemes in PIE not accounted for by reconstructions through the comparative method. He was proven right 50 years later when Hittite was deciphered.
As impressive as his work as a student was, and as much as he himself focused on historical linguistics (which in most senses was the focus of the whole field at the time), Saussure’s legacy lies in ideas he presented through his later lectures. Throughout his career, he lectured on IE, Sanskrit, and even some of the Germanic languages. Then, in 1907, he offered his first Course of General Linguistics, a class he offered only three times between 1907 and 1911. After Saussure’s death, some of his students published a book based on notes from his lectures.
This book, entitled Course in General Linguistics, contains the theories that became the foundation for structural linguistics, wherein language is collected and its elements classified at different levels. Saussure distinguished between an abstract level of language and actual speech. He proposed that the relationship between a signifier (like a word) and what it signified was arbitrary. His ideas on the relationships between the elements of language opened up the fields of phonology, morphology, syntax, and semantics. He put forth theories about dialects and language change based on geography. What’s more, he said it was just as important to study language synchronically, ie as a complete system at a point in time, as it was to look at diachronic, or historic, developments. (His analogy here was that it’s one thing to look at the history of chess and another to understand the rules at a given time.)
Pardon the wall of text. In essence, Saussure revolutionarily encouraged the synchronic study of languages and paved the way for some of the most fundamental disciplines within the field—no linguist escapes undergrad without studying such basic subjects as phonology and syntax.
In the past hundred years, there have been many strides within linguistics. New theories and schools of thought have arisen, and Saussure’s status has diminished, but his influence is never gone. Just try to find an introductory text today that doesn’t mention the arbitrary relation between sign and meaning!