From this question by jess:
Is there a difference between using "number" and "numbers" when referring to multiple numbers? For example, when calling a merchant to inquire about multiple orders, should I say:
I need RMAs for order numbers 1 and 2.
I need RMAs for order number 1 and 2.
This question might sound stupid, but I'm not sure what the main subject is. Is "number" the subject and therefore should I use "numbers"? Or are the order numbers (1 and 2) the subject, so should I keep "number" singular?
Personally, I'd say "for orders number 1 and 2".
while TecBrat answered :
I usually hear that as "order numbers 1 and 2", with the "s". Fumble's comment gives a good way to get around it anyway.
Which one is correct? Which one is wrong and why?