What is a secondary in football?

Answer 1

The 'secondary' are those players on the defense that play in the backfield and cover receivers and backs going out on pass patterns. The secondary consists of two cornerbacks and two safeties and are commonly called 'defensive backs'. Sometimes, when the defense thinks the offense is going to run a pass play, a fifth defensive back will be put into the game to replace a defensive lineman or linebacker. In this case, you might hear the announcer say that the defense is in the 'nickel'. A 'nickel defense' is when there are five defensive backs playing on a particular play.