Clothing for swimming, spoken about as a general category rather than as one item. This is the important difference from 'swimsuit': swimwear is an uncountable word, so you say 'a shop that sells swimwear', never 'a swimwear' or 'two swimwears'. It covers everything in that department — women's one-pieces, bikinis, men's trunks, children's suits — all together.

Clothing for swimming游泳穿的衣物， spoken about as a general category rather than as one item講的時候是當成一個總稱，而不是指單一件。 This is the important difference from 'swimsuit'這是它跟「swimsuit」重要的不同： swimwear is an uncountable wordswimwear 是不可數名詞， so you say 'a shop that sells swimwear'所以你會說「a shop that sells swimwear」， never 'a swimwear' or 'two swimwears'絕不會說「a swimwear」或「two swimwears」。 It covers everything in that department它涵蓋那個類別裡的所有東西 — women's one-pieces, bikinis, men's trunks, children's suits女生的連身泳裝、比基尼、男生的泳褲、小孩的泳衣 — all together全部都算在內。

Because of that, it is the word of shops, labels, catalogues, and adverts: the swimwear section, the summer swimwear range. Ordinary people talking to each other rarely say it; a friend says 'bring your swimsuit', not 'bring your swimwear'. So the word feels commercial and slightly formal, and if you use it in casual conversation you will sound like a shop sign.

Because of that, it is the word of shops, labels, catalogues, and adverts正因如此，它是店家、標籤、型錄和廣告愛用的字： the swimwear section「the swimwear section」（泳裝專區）， the summer swimwear range「the summer swimwear range」（夏季泳裝系列）。 Ordinary people talking to each other rarely say it一般人聊天時很少這樣說； a friend says 'bring your swimsuit'朋友會說「bring your swimsuit」（帶你的泳衣）， not 'bring your swimwear'而不會說「bring your swimwear」。 So the word feels commercial and slightly formal所以這個字給人商業、有點正式的感覺， and if you use it in casual conversation you will sound like a shop sign如果在輕鬆聊天時用它，聽起來會像店家招牌。

English has a whole family built this way — footwear, sportswear, menswear, knitwear — and they all behave the same: category words, uncountable, at home in shops.

English has a whole family built this way英文有一整個家族都是這樣造字的 — footwear, sportswear, menswear, knitwearfootwear（鞋類）、sportswear（運動服）、menswear（男裝）、knitwear（針織服飾） — and they all behave the same它們的用法都一樣： category words, uncountable, at home in shops都是總稱、不可數，也都是店家愛用的字。