Linguistics
In Mandarin, you can't say 'three books' without a special counting word
Chinese requires a classifier, or measure word, between any number and the noun it counts: 'three books' is literally 'three ben books,' where ben is reserved for bound, book-like objects. Mandarin has dozens of these classifiers, sorted by an object's shape or nature, and speakers learn which class a noun belongs to along with the word itself.