Rasmus Kristian Rask was a Danish linguist, philologist and a principal founder of the science of comparative linguistics. In 1818, he first showed that, in their consonant sounds, words in the Germanic languages vary with a certain regularity from their equivalents in the other Indo-European languages. What Rask observed proved to be the basis of a fundamental law of comparative linguistics, which was formally set forth in 1822 by Jacob Grimm.
Rask traveled extensively to study languages, first to Iceland, where he wrote the first grammar of Icelandic, and later to Russia, Persia, India, and Ceylon. Shortly before his death, he was hired as professor of Eastern languages at the University of Copenhagen. Rask is especially known for his contributions to comparative linguistics, including an early formulation of what would later be known as Grimm's Law. He was elected as a member to the American Philosophical Society in 1829.