一般in表示在某个空间内,而inside还有掩盖、受保护的意思.
inside是语气很强的介词.它常用来强调某 人或某事所在地含有某种特殊情况,比如： Inside the castle we'll be safe from the enemy. 在上句中,说话人可能想到的是城堡上厚厚的城墙,或城堡是一个非常坚固的地方.当然,某人 也能把一个相当普通的地方说成是一个牢不可破 的堡垒,比如： He barricaded himself inside the house and started firing at the police.
有时说话人想强调某个地方的空间非常狭窄,比如： It was hot and stuffy inside the prison cell.
inside也可用于与外面的事情(something outside) 作对比： It was quite hot outside the cave but when we were inside, we started to shiver.
除需要特别强调以外,通常都用in.例如, 用于建筑物或建筑物内的房间：in the house, in the office; 用于有围栏或围墙的地方：in the garden, in the courtyard, in the park; 用于交通工具： in the train, in the car, in the bus; 用于江河湖海：in teh sea, in the river, in teh water. 还可用于饮料,如： There's a fly in my lemonade.
尽管人们在 There may be beetles in the lawn 或in the carpet中用in,但是在One sits on the lawn或on the carpet中却要用on.
当谈到服装时,用in和用inside在句子意思 上就出现了有趣的区别.通常用in.
但是,人穿着衣裳感到不舒适或感到受到约束(如 同身处囹圄),这时用inside 就会非常生动有效地 表达此种感觉,例如：
The little girl felt like a prisoner inside her starched new dress. Mary felt like a packaged chicken inside her corsets.
当然,有时用in和inside都不合适,例如： She was kept in/inside the walls of the prison.
此句的意思是她和水泥一起被填进了墙里.这种 情况可能有,但是不会经常出现.