corner stone
 奠基石


 Cor·ner n.
 1. The point where two converging lines meet; an angle, either external or internal.
 2. The space in the angle between converging lines or walls which meet in a point; as, the chimney corner.
 3. An edge or extremity; the part farthest from the center; hence, any quarter or part.
    From the four corners of the earth they come.   --Shak.
 4. A secret or secluded place; a remote or out of the way place; a nook.
    This thing was not done in a corner.   --Acts xxvi. 26.
 5. Direction; quarter.
    Sits the wind in that corner!   --Shak.
 6. The state of things produced by a combination of persons, who buy up the whole or the available part of any stock or species of property, which compels those who need such stock or property to buy of them at their own price; as, a corner in a railway stock. [Broker's Cant]
 Corner stone, the stone which lies at the corner of two walls, and unites them; the principal stone; especially, the stone which forms the corner of the foundation of an edifice; hence, that which is fundamental importance or indispensable. “A prince who regarded uniformity of faith as the corner stone of his government.” --Prescott.
 Corner tooth, one of the four teeth which come in a horse's mouth at the age of four years and a half, one on each side of the upper and of the lower jaw, between the middle teeth and the tushes.