The usual way of making a singular noun into a plural noun is to add s, but a lot of words need altering before the s is added.
If a noun ends in ch, sh, x or ss, we usually add es.
If a noun ends in a consonant and y we usually delete the y and add ies.
Note that if the letter before the y is a vowel then we just add s.
If a noun ends in f or fe we usually delete the f or fe and add ves.
Note that if the noun ends in double f then we just add s.