可以说 room door（房门），即直接用名词作定语；但不能说 room’s door，不过说成 the door of the room 则完全可以。

类似的例子如：

▲apartment door

I locked my apartment door before leaving for work. 我上班之前锁上了家门。

▲bedroom door

The bedroom door banged shut. 卧室的门砰的一声关上了。

I woke up to hear the bedroom door being opened slowly. 我醒过来，听见卧室的门慢慢地被推开。

▲car door

I shut my finger in the car door. 我的手指让汽车门给夹住了。

The car door was shorn off in an accident. 汽车车门在一次事故中被撞掉。

▲cathedral door

There’s a long flight of steps ascending (= leading up) to the cathedral doors. 要往上走上很长一段台阶才能到达大教堂的门前。

▲church door

We used white flowers and green leaves to ornament the church door for the wedding. 为了举行婚礼，我们用白花和绿叶美化了教堂的门。

▲cupboard door

He cracked his head on the cupboard door. 他的头撞在了橱柜的门上。

▲fridge door

Did the fridge door close completely? 冰箱门是否完全关好了。

▲refrigerator door

I pulled the handle and opened the refrigerator door. 我拉住冰箱的门把打开冰箱。

▲hall door

“There is somebody at the hall door.” “I’ll go and open it.” “有人在大厅门外面。”“我去开门。”

▲room door

It was too late now for Blake to lock his room door. 这会儿布莱克再锁房门已太晚了。

▲shop door

Two shoppers were injured in the stampede as shop doors opened on the first day of the sale. 第一天减价商店开门的时候，有两名购物者在拥挤中受了伤。

▲stage door

The actress was confronted by a large group of reporters as she left the stage door. 那位女演员在离开后台门口时被一群记者拦住了。

▲train door

Train doors have handles on the inside. They are stiff so that they cannot be opened accidentally. 火车车门内侧有把手。把手都很紧，防止意外开启。