long 可以指两个线段之间的距离，指的是长度，它的名词是length，(长度) 例如，how long is the bridge? how long is the river? long还可以指时间的长短，例如，how long it will take you to finish the task? 而far 往往指的是距离上的远近，例如，how far is it from your school to your home?