Rules on how to change singular nouns into their plural forms

This time I'll be sharing with you the simple steps on how to change singular nouns into their plural forms. This so called rules have been used until now, though there are a few additions, which I will also be mentioning below.

Rule #1

Simply add 's' to some singular nouns. Remember, it's only for some nouns, not all.

jail-jails

book-books

Rule#2

Add 'es' to nouns ending with a sibilant sound such as s, sh, ch, x or z. Sibilant sound is just like the sound of a whisper.

church-churches

box-boxes
dish-dishes

But the plural form of the noun bus can be written as buses or busses.

Rule #3

Add 's' to a noun ending in 'o' which is preceded by a vowel letter.

radio-radios

bamboo-bamboos

Rule #4

Add 'es' to a noun ending in 'o' that is preceded by a consonant letter.

potato-potatoes

tomato-tomatoes

Rule #5

However, if it's a musical term, just add 's.'

piano-pianos

tempo-tempos

cello-cellos

alto-altos

soprano-sopranos

Now, here's one question that has baffled a few. What is the plural form of photo? I go with what many considered correct, and it's photos. The word photo is just the short form of photograph, which takes the plural form photographs. I think it serves as the best explanation to this.

However, there are also other nouns ending in 'o' preceded by a consonant letter that have two plural forms. Adding 's' or 'es' is considered correct. Here are a few examples of them.

mango-mangos/mangoes
mosquito-mosquitos/mosquitoes

tornado-tornados/tornadoes

buffalo-buffalos/buffaloes

Rule #6

Add 's' to nouns ending in 'y' preceded by a vowel letter.

key-keys

day-days

Rule #7

But change 'y' to 'i' then add 'es' if 'y' follows a consonant letter.

baby-babies

lily-lilies

Rule #8

For some nouns ending in 'f' or 'fe', change 'f' and 'fe' into 'v', then add 'es.'

calf-calves

wife-wives

life-lives

But nouns like safe, cliff and roof form their plural by adding 's'.

safe-safes

cliff-cliffs

roof-roofs

These example of nouns, however, can have two plural forms.

dwarf-dwarfs/dwarves

wharf-wharfs/wharves

Rule #9
For nouns ending in 'ix' or 'ex', change them into 'ices' or just simply add 'es'.

index-indices/indexes

appendix-appendices/appendixes

Rule #10
For some nouns of Latin origin ending in 'us', simply change 'us' to 'i'.

alumnus-alumni

radius-radii

But these following nouns can have two plural forms.

cactus-cacti/cactuses

octopus-octopi/octopuses

Rule #11

For compound nouns not separated by a hyphen, just add 's' or 'es'.

jailhouse-jailhouses

doorknob-doorknobs

Rule #12

For nouns with modifiers, add 's' or 'es' to the nouns.

father-in-law - fathers-in-law (not father-in-laws)

Rule #13

For some nouns of Latin origin ending in 'is', just change 'is' to 'es'.

crisis-crises

oasis-oases

Rule #14

For some nouns of Latin origin ending in 'a', just add 'e'.

alumna-alumnae

nebula-nebulae

Rule #15

For some nouns of French origin, just add 'x'.

tableau-tableaux

chateau-chateaux

Rule #16 

Just add apostrophe s to letters and numbers.

A-A's

5-5's