[card_zero]

Doesn't that just say "a pair of pants"? Or literally one line pants.

[thaumasiotes]

条 is the appropriate measure word for pants; they're plural in English, but uncountable (like other nouns) in Chinese.

You could translate it as "a pair of pants", and that's the appropriate way to put it in English, but really it says "one pants".

[card_zero]

I guess the measure word works equivalently to a unit of measurement, then. One bottle of beer, one sack of sugar, one 条 of pant.

[thaumasiotes]

Correct. In Chinese all nouns require them.

(It's not the case, however, that all measure words require nouns. 天 ("day") and 年 ("year") are measure words that are almost always used on their own. There might be an implicit notion of "one day of time" or similar.)

[seanmcdirmid]

You wouldn't be surprised how often chinese learners say 一双裤子 (one pair of pants) rather than 一条裤子 (one long slender flowing pants).

[thaumasiotes]

All learners of Chinese, or just the ones whose native language is English?

I figure the most natural mistake to make when counting pants is to use 件, since that's the measure word that applies to "clothes", but you'd have to already know at least some Chinese in order to make that mistake.

[seanmcdirmid]

Ah, the ones coming from English of course. I don't have much experience in how Koreans or Russians learn Chinese (although I had plenty of non-English classmates when I took language lessons at PKU).

I'm thinking more Kouyu than writing. If I didn't think hard about it, I might say yi shuang kuzi or even, for some reason, yi jian kuzi.