Pajamas = 睡衣 [shuì yī]
A cream-colored cat with a dark tail sleeps on its back in a green zip-up hoodie, hood pulled up. Those are its 睡衣.
睡衣 (shuìyī) means “pajamas” or “nightclothes.” 睡 is to sleep and 衣 means clothes.
Count a matching set with 套 (tào): 一套睡衣. To put them on is 穿睡衣 (chuān shuìyī).
我一回家就换上睡衣。 — Wǒ yì huí jiā jiù huàn shàng shuìyī. — I change into my pajamas as soon as I get home.
他穿着睡衣去买早饭。 — Tā chuānzhe shuìyī qù mǎi zǎofàn. — He went to buy breakfast in his pajamas.