Some words ending in o that form their plural by adding s only include: pianos, duos, solos, tacos.
Nouns that end in 'o' in their singular form can take an 's' or an 'es' for their plural form. Some examples:echo to echoeshero to heroespotato to potatoesveto to vetoesauto to autosphoto to photosstudio to studiospiano to pianos
Nouns ending with -o that form the plural by adding -s to the end of the word are:autoscameoskangarooskilosmemosphotospianossolosstudiostattoosvideoszoos
Some plural words ending in "o" are photos, pianos, casinos, and zoos.
plural: pianosMost words ending with an 'o' usually take '-es' to form the plural, but some words take '-s', e.g. pianos, radios, videos, etc.
Cello > cellosDisco > discosRadio > radiosPhoto > photosPatio > patios
Because there is no standard rule for words ending in -o.
The plural form photos is an exception to the rule that words which end with -o preceeded by a consonant have -es added to create the plural form.
Examples of nouns ending with -o that just add -s to form the plural are:auto - autoscameo - cameoskangaroo - kangarooskilo - kilosmemo - memosphoto - photospiano - pianossoprano - sopranosstudio - studiostattoo - tattoosvideo - videoszoo - zoos
The nouns ending in ch, sh, s, x, and z add -es to the end of the word to form the plural. Only some nouns ending in o use -es to form the plural.Examples:church, churcheswish, wishesdress, dressesbox, boxeswaltz, waltzespotato, potatoeshero, heroes
Some nouns ending with an 'o' preceded by a consonant add 'es' to the end of the word to form the plural; for example:tomato - tomatoespotato - potatoeshero - heroesecho - echoesbuffalo - buffaloesmosquito - mosquitoesMost nouns ending with an 'o' simply add 's' to the end of the word to form the plural; for example:zero - zeroszoo - zoosstudio - studiosradio - radiosavacado - avacadosauto - autos
Unfortunately there is no simple rules for using 's' or 'es' to change nouns ending in 'o' into the plural form. How fortunate we are to live in the age of spell check, otherwise you need a hard copy dictionary or a good memory. Some examples are:echoesheroespotatoestomatoesvetoesautoskangarooskilosphotostattoos