patio - patios
Nouns ending with -o that form the plural by adding -s to the end of the word are:autoscameoskangarooskilosmemosphotospianossolosstudiostattoosvideoszoos
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.
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
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.
es, like echo- e choes that would be plural
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
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
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
There's no general rule for forming the plural forms of words ending in -o. Many plural forms are formed by adding -es, e.g. tomato - tomatoes, potato - potatoes, hero - heroes. Other plurals are formed simply by adding -s, e.g. zero - zeros, memo - memos, hippo - hippos.