What is the function of classifiers and when should I use them?
In other asian languages such as Chinese and Japanese, you can only place a classifier before a noun when you are counting it, but I've noticed that this doesnt hold true for Vietnamese, since I've seen many sentences in which classifiers have been used without any counting (e.g: Con cá = The fish).
You add the classifier/counting word to turn it into a definite noun (the singular x). You add những/các before the definite noun to turn it into a plural, or you can replace những with a number to mean any number of indefinite nouns.
Cá = fish
Con cá = the fish (singular)
Một con cá = a fish
Những con cá = the fish (plural)
Đàn ông = man/men
Người đàn ông = the man
Một người đàn ông = a man
Những người đàn ông = the men, such men
Actually from what I understand, when you are counting nouns, you must add a classifier between the number and the noun in question. Ex: Ba (3) Cuốn (Classifier for books) Sách (Book) = 3 books. Hai (2) Con Cá = 2 Fish. Sáu (6) xe (Classifier for vehicles) hơi (car, also known as ô tô) = 6 cars.