long 可以指兩個線段之間的距離,指的是長度,它的名詞是length,(長度) 例如,how long is the bridge? how long is the river? long還可以指時間的長短,例如,how long it will take you to finish the task? 而far 往往指的是距離上的遠近,例如,how far is it from your school to your home?