I think undies is short for underpants or underwear.

我觉得 undies 是内裤或内衣的简称。

Yes. And we can refer to our underwear as 'smalls' or 'undies'.

对。内衣可以用smalls和undies来表达。

I see. So you don't say 'one small' or one 'undy'.

我明白了。所以不能说one small或者one undy。

We wear on our bottom part of our bodies " a pair of undies" .

我们穿在身体下部的“内裤”。

I put five pairs of undies in here, and now there are four.

我放了五条内裤进去，现在只剩四条。

No, you don't. Smalls and undies are always used in the plural and they mean underwear.

对，不能这么说。这两个词在表示“内衣”这个意思时要用复数形式。

You can say undies, right? My undies.

你可以说内裤， 对吧？我的内裤。

Well, smalls and undies can look good too, even if not many people will see them.

虽然大多数人看不到，但是内衣也可以很漂亮。

Undies. That's easy to remember because it refers to what we wear under our clothes — undies.

内衣。这很容易记，指我们在衣服里面穿的，所以就是内衣。

Then let's find your precious undies.

那我们就把你的宝贝底裤找出来吧。