Underpants; underwear such as briefs or panties, referring to undergarments worn next to the skin.
子供のパンツが汚れたので、新しいものを買った。
The child's underwear got dirty, so I bought a new pair.
温泉ではタオルを巻いてパンツを見せないのが礼儀だ。
At hot springs, it's polite to wrap a towel and not show your underwear.
男性用のパンツは素材や形が色々ある。
Men's underwear comes in various materials and cuts.
Trousers or pants (esp. women's trousers); can also mean shorts or trunks (e.g., swim trunks) depending on context.
彼女は新しいパンツを買って出かけた（ここではズボンの意味）。
She bought new pants and went out (here meaning trousers).
海へ行くときは水着のパンツも忘れずに持っていって。
When you go to the beach, don't forget to bring your swim trunks.
職場ではカジュアルすぎるパンツは避けた方がいい。
At work it's better to avoid pants that are too casual.