in和into都可作介词,与“里面”有关,但用法有别.
in是表示物体位置的静态介词,表示“在……里面”.
They are sitting in the room.他们正坐在房间里.
The boy is in Class 2,Grade 3.这个男孩在三年级二班.
into是表示动作方向的动态介词,表示“到……里面去”,常与表示动作的动词（如come,go,run,rush等）连用.
He ran into the room just now.刚才他跑进了房间.
They all jumped into the sea and swam to the island.他们都跳进了海里,向那个岛游过去.
有些动词（如put,fall,throw等）既可用in,也可用into,这时in同into一样,也表示动态.
Can you help me put these things in the basket?
你能帮我把这些东西放到篮子里吗?
The boy fell in the water.这个男孩掉进水里了.
in还可用作副词,意为“在家、往里面”,而into不能.
Is Tom in?汤姆在家吗?
May I come in?我可以进来吗?