verb

• (transitive) To make simpler, either by reducing in complexity, reducing to component parts, or making easier to understand.
  "In ancient times there existed in the region of the Tung-chia River 佟佳江 in present Liaoning a people called Kao-chü-li 高句驪. In the fifth century they moved their capital to P’ing-jang. The name of the country was simplified to Kao-li 高麗 (Korea)."
• (intransitive) To become simpler.
  "Thus, throughout the nineteenth century, linguists generally held that more grammatically complex languages were older and that languages tended to simplify over time—the four grammatical cases of German as contrasted with the seven of Latin, for example."