Jakob Ludwig Karl (ˈjaːkɔp ˈluːtvɪç karl), 1785–1863, and his brother, Wilhelm Karl (ˈvɪlhɛlm karl), 1786–1859, German philologists and folklorists, who collaborated on Grimm's Fairy Tales (1812–22) and began a German dictionary. Jakob is noted also for his philological work Deutsche Grammatik (1819–37), in which he formulated the law named after him