plurals

English is a schizophrenic language that borrows from a lot of other languages, and the rules for making singular
nouns into plural nouns are varied and complex. There are rules, and then there are exceptions to those rules, and then
there are exceptions to the exceptions.
If you grew up in an English−speaking country or learned English in a formal school setting, you're probably familiar
with the basic rules:

1. If a word ends in S, X, or Z, add ES. "Bass" becomes "basses", "fax" becomes "faxes", and "waltz" becomes
"waltzes".
2. If a word ends in a noisy H, add ES; if it ends in a silent H, just add S. What's a noisy H? One that gets
combined with other letters to make a sound that you can hear. So "coach" becomes "coaches" and "rash"
becomes "rashes", because you can hear the CH and SH sounds when you say them. But "cheetah" becomes
"cheetahs", because the H is silent.
3. If a word ends in Y that sounds like I, change the Y to IES; if the Y is combined with a vowel to sound like
something else, just add S. So "vacancy" becomes "vacancies", but "day" becomes "days".
4. If all else fails, just add S and hope for the best.

(I know, there are a lot of exceptions. "Man" becomes "men" and "woman" becomes "women", but "human" becomes
"humans". "Mouse" becomes "mice" and "louse" becomes "lice", but "house" becomes "houses". "Knife" becomes
"knives" and "wife" becomes "wives", but "lowlife" becomes "lowlifes". And don't even get me started on words that
are their own plural, like "sheep", "deer", and "haiku".)