[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.)