Lila Gleitman, whose pioneering work in linguistics and cognitive science expanded our understanding of how language works and how children go about learning it, died August 8 at a hospital in Philadelphia. She was 91.

According to Dr. Gleitman, the structures, or syntax, of language are hardwired into the brain from birth, and that children already have a sophisticated grasp of how they work. “The study of language acquisition was her field in a special sense,” said Dr. Noam Chomsky, a colleague. “She virtually created the field in its modern form and led in its impressive development ever since.”