In English, you can say “There is a flock of birds” or just “There are five birds” — the measure word is optional. In Chinese, it never is. Whenever a number (or a demonstrative like “this” or “that”) comes before a noun, a measure word has to sit between them.

There are over two hundred measure words in Chinese, and most nouns pair with one specific to their meaning — which is exactly why they’re such a common sticking point for learners.

Every noun, even a single, countable one, needs a measure word in Chinese.

With time nouns, the measure word can sometimes vanish entirely — and the reason is more about rhythm than grammar. Chinese speech has a soft preference for even-numbered syllables. A one-syllable time word already sits at an odd count, so the measure word usually gets dropped to keep things balanced — even once the number climbs into the double digits.

A two-syllable time noun, though, is already at an even count — so the measure word usually stays, to keep that even rhythm rather than break it.