-es

Concise Oxford English Dictionary © 2008 Oxford University Press:
-es1

▶suffix

• 1 forming plurals of nouns ending in sibilant sounds: kisses.

• 2 forming plurals of certain nouns ending in -o: potatoes.

– origin var. of -s1.

Concise Oxford English Dictionary © 2008 Oxford University Press:
-es2

▶suffix forming the third person singular of the present tense.

• 1 in verbs ending in sibilant sounds: pushes.

• 2 in verbs ending in -o (but not -oo): goes.

– origin var. of -s2.