1
a stair (as a single step)
stair 作为可数名词，指单个梯级，常用单数。
Be careful, there is a broken stair.
小心，有一个梯级坏了。
楼梯的梯级
先理解核心含义，再看它在真实句子里的用法。
楼梯的梯级
a single step in a set of stairs
Be careful, there is a broken stair.
小心，有一个梯级坏了。
楼梯中的一级台阶
A single step in a staircase.
用于在楼梯上升或下降时支撑脚的地方
support consisting of a place to rest the foot while ascending or descending a stairway
一系列台阶；楼梯
A series of steps; a staircase.
She carefully climbed the narrow stair to the attic.
她小心翼翼地爬上通往阁楼的狭窄楼梯。
The first stair creaked loudly when I stepped on it.
我踩上第一级台阶时，它发出很大的吱嘎声。
He slipped on the top stair and nearly fell.
他在最上面一级台阶滑倒了，差点摔下来。
stair 作为可数名词，指单个梯级，常用单数。
Be careful, there is a broken stair.
小心，有一个梯级坏了。
复数形式 stairs 指整段楼梯，常与定冠词连用。
She ran up the stairs to her room.
她跑上楼梯去了她的房间。
动词 go 与 up/down 搭配表示上下楼梯，stairs 常以复数形式出现。
He tripped while going down the stairs.
他下楼梯时绊倒了。
Not this
I need to go up the stair.
Use this
I need to go up the stairs.
中文常将“楼梯”视为单数，但英语中表示整个楼梯时通常用复数 stairs。
Not this
He stair up to the second floor.
Use this
He walks up the stairs to the second floor.
Stair 是名词，不能用作动词；应使用动词短语 walk up 或 go up。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
一段楼梯
A flight of stairs leads to the rooftop.
一段楼梯通向屋顶。
爬楼梯
He climbs the stairs every morning for exercise.
他每天早晨爬楼梯锻炼身体。
楼梯顶部
The cat was sitting at the top of the stairs.
那只猫坐在楼梯顶部。
楼梯扶手
Please hold the stair rail when carrying the baby.
抱孩子的时候请扶着楼梯扶手。
楼梯地毯
The stair carpet is worn out and needs replacing.
楼梯地毯磨损了，需要更换。
楼梯安全门
They installed a stair gate to keep the toddler from falling down the stairs.
他们安装了楼梯安全门，防止幼儿从楼梯上摔下来。
在楼下仆人区；在仆人区工作的
She spent many years working below stairs as a cook.
她在楼下厨房当厨师，工作了很多年。
有一位女士确信闪闪发光的东西都是金子，她正在买一座通往天堂的阶梯。
She climbed the stairs to the attic to find the old photo album.
她爬上楼梯到阁楼去找那本旧相册。
Use stair naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
stair 听起来像 stare（盯着看），想象你站在楼梯前，盯着每一级台阶看——stair 就是“梯级”。
语域：neutral 常见场景：日常交谈、建筑说明 stair 作名词时，通常指单个梯级；在日常口语和书面语中，复数 stairs 更常用来指整段楼梯。整体属于中性、通用的表达，正式或非正式场合都比较常见。
常用复数形式stairs
Dictionary facts from DICTIONARY_API_DEV, ECDICT, WIKTIONARY.