1.downstairs用作形容词时,在句中一般用作定语,可置于被修饰词之前或之后。
2.downstairs无比较级和最高级。

用作定语
▲～+n./pron.
The downstairs part isn't interesting, but the upper floors are nice.楼下没什么意思,但是楼上很不错。
The downstairs rooms are not as quiet as the upstairs ones.楼下房间没有楼上房间安静。
▲n.+～
Our neighbour downstairs is very noisy.我们楼下的邻居非常吵闹。
She leaned over the balustrade and shouted to the man downstairs.她俯身在阳台栏杆上对楼下的人们喊着。

downstairs有时还可用作名词,意为“楼下”。例如:
We haven't painted the downstairs yet.我们还没有给楼下涂漆。

［反义词］ adv. & adj. upstairs

1.downstairs用作副词的意思是“在楼下”,还可表示“向〔往〕楼下”。作“在楼下”解时,常与静态动词(如be, live, wait等)连用; 作“向〔往〕楼下”解时,往往与动态动词(如come, fall, go, walk等)连用,表示运动的方向。
2.downstairs无比较级和最高级。

用作状语
John's father is waiting downstairs.约翰的父亲在楼下等着。
He went downstairs to breakfast.他下楼去吃早饭了。
用作表语
Is anyone downstairs?楼下有人吗?
用作宾语补足语
I forgot to bring the hat downstairs with me.我忘记把帽子带下楼来了。

downstairs, downstair
downstair原用作形容词,意为“楼下的”; downstairs原用作副词,意为“朝楼下”。但在现代英语中, downstair已逐渐废弃不用; downstairs则既可用作副词,也可用作形容词。
下面两句意思不同:
She went down the stairs.
她顺着楼梯走下去。
She went downstairs.
她下楼了。