in AM, use 美国英语用 football
										-  美式橄榄球(运动);美式足球(运动)
 American football is a game similar to rugby that is played by two teams of eleven players using an oval-shaped ball. Players try to score points by carrying the ball to their opponents' end of the field, or by kicking it over a bar fixed between two posts.
 
-  美式橄榄球用球
 An American football is an oval-shaped ball used for playing American football.