1
a pair of sweatpants
sweatpants 是复数名词，表示“一条”时用 a pair of。
She bought a new pair of sweatpants for the gym.
她为去健身房买了一条新运动裤。
运动裤
先理解核心含义，再看它在真实句子里的用法。
运动裤
loose comfortable trousers with elastic cuffs, often worn for sports or leisure
She bought a new pair of sweatpants for the gym.
她为去健身房买了一条新运动裤。
运动裤；宽松紧口长裤
loose-fitting trousers with elastic cuffs; worn by athletes
After work, I like to change into sweatpants and relax on the sofa.
下班后，我喜欢换上运动裤，在沙发上放松。
She packed a pair of sweatpants for the long flight.
她为长途飞行打包了一条运动裤。
He wore sweatpants to the morning yoga class.
他穿着运动裤去上晨间瑜伽课。
sweatpants 是复数名词，表示“一条”时用 a pair of。
She bought a new pair of sweatpants for the gym.
她为去健身房买了一条新运动裤。
sweatpants 前不加 a/an，动词用复数形式。
He wears sweatpants at home on weekends.
他周末在家穿运动裤。
in + 服装名词表示“穿着…”的意思。
I saw her in sweatpants at the market.
我在市场看到她穿着运动裤。
Not this
This sweatpants is very comfortable.
Use this
These sweatpants are very comfortable.
sweatpants 是复数名词（与 trousers、scissors 相同），永远用复数形式，所以指示代词和动词都要用复数。
Not this
I bought a new sweatpants yesterday.
Use this
I bought a new pair of sweatpants yesterday.
sweatpants 是复数名词，前面不能直接加 a/an；表示“一条运动裤”时要用 a pair of，或用复数形式（如 I bought new sweatpants）。
Not this
He went to the gym with sweatpants.
Use this
He went to the gym in sweatpants.
表示“穿着某衣物”时，英语用 in（或 wearing），不用 with；with 表示“随身带着”或“和……一起”，会改变原意。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
一条运动裤
She packed a pair of sweatpants for the long journey.
她为长途旅行打包了一条运动裤。
穿运动裤
Many people wear sweatpants when they work from home.
很多人在家办公时穿运动裤。
宽松的运动裤
He chose loose-fitting sweatpants for the dance rehearsal.
他选了宽松的运动裤去参加舞蹈排练。
运动裤和连帽衫（休闲搭配）
She wore sweatpants and a hoodie to the coffee shop.
她穿着运动裤和连帽衫去咖啡店。
换上运动裤
After work, I like to change into sweatpants and relax.
下班后，我喜欢换上运动裤放松一下。
运动裤是失败的标志——你已经失去了对生活的掌控。
He showed up to the meeting in sweatpants.
他穿着运动裤来开会。
Use sweatpants naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
sweat=汗 + pants=裤子：运动出汗时穿的宽松长裤，裤脚有松紧带，记住 sweatpants 就是运动裤。
语域：informal 常见场景：居家休闲、健身运动、休闲外出 sweatpants 通常用于非正式场合，多指居家、健身或日常休闲时穿的运动长裤；在正式场合一般不会使用。
sweatpants 本身是复数形式。
Dictionary facts from ECDICT, WIKTIONARY, WORDNET.