/z/ if the singular ends in a vowel
or in a voiced consonant different
from a sibilant.
/s/ if the singular ends in a
voiceless consonant other than a
sibilant.
Spelling
-s
-es if the singular ends in a sibilant
that is not already followed by -e.
- ies if the singular ends in -y.
-ys if the singular ends in -ay, -ey,
-oy or if the item is a proper noun.
-s if the singular ends in -o, but with same
nouns the plural is -es (echoes, heroes,
potatoes). In a few cases, there is
variation (buffalo(e)s, cargo(e)s,
volcano(e) s.