Page 546 - Practical English Usage 3ed - Michael Swan, Oxford

Singular
... ch/sh/s/x/z
church crash bus box buzz
Plural
... ches/shes/ses/xes/ZI!S
churches crashes buses boxes buzzes
singular and plural (1): regular plurals 523
523 singular and plural (1): regular plurals
The plural of most nouns is made by just adding -s to the singular. But there are some special cases.
1 plural of nouns ending in consonant + y
If the singular ends in consonant + y (for example -by, -dy, -ry, -ty), the plural
is normally made by changing y to i and adding -es.
Singular
... consonant + y
baby lady ferry
Plural
... consonant + ies
babies ladies ferries
party
If the singular ends in vowel + y (e.g. day, boy, guy, donkey), the plural is made
by adding -s (days, boys, guys, donkeys).
Proper names ending in consonant + y usually have plurals in -ys. Do you know the Kennedys? (NOT ••• the Kertnedies,!)
I hate Februarys.
2 plural of nouns ending in -sh, -ch, -s, -x or -z
If the singular ends in -sh, -ch, -s, -x or -z, the plural is made by adding -es.
parties
Nouns ending in a single -z have plurals in -zzes: quiz/quizzes, fez/fezzes.
3 plural of nouns ending in -0
Some nouns ending in -0 have plurals in -es. The most common:
Singular Plural
echo echoes hero heroes negro negroes
Singular
potato tomato
Plural
potatoes tomatoes
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