a/an 侧重人或物的类别 a little boy is eating an apple.
one 侧重人或物的数量 one boy can do it.
ago 不可单独使用。“一段时间+ago”表示从现在算起的“.........之前”（用于一般过去时）Eg: they worked in the factory ten years ago.
before 可以单独使用，意为“以前”（用于现在完成时）I have this film before.
“一段时间+before”表示从过去某一时间算起的“..........之前”（用于过去完成时）He said he had seen this film two weeks before.
I've just eaten it.
just 还可以表示“正好，恰好”，起强调语气的作用。He's just at school gate. just now 意为“刚才，不久以前”；just then 意为“就在那时”
I met one of my friends in the street just now.
Just then he came out of his office.
Why? 为什么 表示........的原因
The reason why he was late is that his mother was ill.
I don't want to play with you any more.
play with 跟......玩耍 do you often play with your friends on Sundays?
play the violin play the piano
play basketball play football
play computer games
not....any more/no more 多指“次数”或“数量”上不再延续，多与短暂性动作连用。 He won't go to the dangerous house any more.
=He will no more go to the dangerous house
not....any longer/no longer 侧重于“时间”上不再延续，多与延续性动词连用。 Hurry up! I can't wait any longer. = Hurry up! I can no longer wait.
family 指家庭整体时，视为单数，谓语动词用单数形式hHis family is large
family 指家庭成员时，视为复数，谓语动词用复数形式His family are all well home 指“家”，指某人出生或居住的地方，含有感情色彩
in the north of........(west east centre)