Because of the long chain molecular structure of rubber and the weak secondary force between molecules, the rubber material has a unique viscoelastic property, so it has a good effect.

The chengguan are a secondary security force employed to take pressure off the police by enforcing regulations, but are widely feared for their heavy-handedness.

NASDAQ, New York's other big stock exchange, has evolved from a secondary market dealing mainly in technology and start-up companies to a global force.