Grimm, Jakob, 1785-1863, German philologist and folklorist, a founder of comparative philology. His interest in the relationship among Germanic languages led to his formulation of Grimm's law. His German grammar (1819-37) and his German Mythology (1835, tr. 1880-88) were works of first importance. He is best known, however, for his two-volume compilation of German folk tales, known as Grimm's Fairy Tales (1812-15, rev. eds. 1819-57), which he collected with his brother, Wilhelm Grimm, 1786-1859, and which did much to encourage the romantic revival of folklore. The brothers Grimm also planned and inaugurated the great German dictionary (16 vol., 1854-1954).