Yes.
It is illegal to impede the progress of any player, regardless of whether the player is in possession of the ball, by sticking your leg out and attempting to trip them. The penalty is 10 yards.
No. Tripping by a blocker for the ball carrier or by a defender trying to tackle the ball carrier is illegal and is a 10 yard penalty.
Yes
Tripping
believe it or not it's just called tripping
It is a ten yard penalty - Vikings vs. Steelers 10/25/09
A penalty is declined in football when the team that committed the penalty would benefit more from the result of the play than from the penalty yardage.
The maximum distance that can be given as a penalty in American football is half the distance to the opponent's goalline; for example, if you were on the 15-yard line and received 10 yards of penalty, the maximum you could gain is 7.5, or 8 yards rounded.
There is no penalty for that
Pittsburgh and phillidelphia, November 10,1940
There is no evidence that such a penalty exists in any football league currently.
No, a holding penalty in football cannot be declined by the opposing team.
The football penalty was declined by the team because they chose not to accept the penalty and instead opted to keep the result of the play as it was.