1
sit on a chair
表示坐在椅子上时，介词用 on。
Please sit on the chair and wait for the doctor.
请坐在椅子上等医生。
椅子
先理解核心含义，再看它在真实句子里的用法。
椅子
A piece of furniture for one person to sit on, with a back and usually four legs.
Please sit on the chair and wait for the doctor.
请坐在椅子上等医生。
供一人坐的家具,设有座面、腿或轮子、靠背,有时带扶手。
An item of furniture used to sit on or in, comprising a seat, legs or wheels, back, and sometimes arm rests, for use by one person.
一个人的座位,带有靠背
a seat for one person, with a support for the back
管弦乐队中特定乐师的演奏座位。
The seating position of a particular musician in an orchestra.
教授的职位
the position of professor
Please pull up a chair and join us at the table.
请拉一把椅子过来，和我们一起坐在桌旁。
AI contextual example
She was appointed to the chair of modern history last year.
她去年被任命为现代史教授。
AI contextual example
The chair adjourned the meeting after a long discussion.
主席在长时间讨论后宣布休会。
AI contextual example
he put his coat over the back of the chair and sat down
他把外套搭在椅背上,然后坐了下来。
WordNet
表示坐在椅子上时，介词用 on。
Please sit on the chair and wait for the doctor.
请坐在椅子上等医生。
chair 指会议或组织的主持人或主席，不区分性别。
She was appointed chair of the environmental committee.
她被任命为环境委员会的主席。
take the chair 是“主持会议”的固定说法，不是“搬椅子”。
He took the chair and called the meeting to order.
他主持会议，宣布会议开始。
此处的 chair 指教授职位或讲席。
Professor Lee holds the chair of Ancient History at the university.
李教授在该大学担任古代史讲席教授。
Not this
I sat on chair.
Use this
I sat on a chair.
汉语中名词没有冠词系统，学习者容易在可数名词单数前漏掉限定词。chair 是可数名词，表示“一张椅子”时必须说 a chair 或 the chair，不能在没有任何限定词的情况下单独使用。
Not this
He sat at the chair.
Use this
He sat on the chair.
介词 at 常接桌、台等平面或地点（如 sit at a desk），表示“坐在椅子上”的姿势时用 on（有扶手的椅子也可用 in）。汉语“在椅子上”的“在”容易误译为 at，导致此错。
Not this
I have two chair.
Use this
I have two chairs.
汉语名词没有单复数变化，英语可数名词在数量大于一时要用复数形式。chair 的复数是 chairs，因此 two chairs 才是正确表达。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
电椅（刑具）
The murderer was sentenced to the electric chair.
谋杀犯被判处电椅死刑。
摇椅
She sat in a rocking chair and read a book.
她坐在摇椅上看书。
安乐椅
He relaxed in an easy chair after work.
他下班后在安乐椅上休息。
折叠椅
They set up folding chairs for the guests.
他们为客人准备了折叠椅。
主持会议，担任主席
Professor Li took the chair at the meeting.
李教授主持会议。
主持会议；担任主席
Professor Wang will take the chair at the meeting tomorrow.
王教授将在明天的会议上担任主席。
处于主持地位；掌权
During the debate, the senior senator was in the chair.
在辩论期间，资深参议员担任主席。
（人员或职位的）频繁变动
The company has been playing musical chairs with its executives all year.
这家公司全年都在频繁更换高管。
Use chair naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
椅子的英文chair，可拆成c+hair，c像弯曲的椅子，hair是头发，想象弯曲的椅子上有头发。
椅子为日常家具用语；主席多用于会议或组织；教授席位用于学术界；电椅用于法律执行语境。整体语域中性，具体意义需结合语境判断。
注意：作名词时通常可数；表示“教授职位”时后接of或in。
Dictionary facts from DICTIONARY_API_DEV, ECDICT, WIKTIONARY.