Nouns that end in 'o' in their singular form can take an 's' or an 'es' for their plural form. Some examples:
Some plural words ending in "o" are photos, pianos, casinos, and zoos.
Some words ending in o that form their plural by adding s only include: pianos, duos, solos, tacos.
es, like echo- e choes that would be plural
potato - potatoes tomato - tomatoes hero - heroes zero - zeros halo - halos whacko - whackos cameo - cameos patio - patios oreo - oreos
There are two types of plural noun forms, regular nouns and irregular nouns.A regular plural is a word that forms the plural by adding an -s or an -es to the end of the word.An irregular plural is a word that forms the plural in some other way.Examples of regular plural nouns:apple: applesbox: boxeschurch: churchesdog: dogsegg: eggsglass: glassesExamples or irregular plural nouns:baby: babies (nouns ending in -y preceded by a consonant, change the -y to -ies)lady: ladiescalf: calves (nouns ending in -f or -fe, but not -ff or -ffe, change the -f or -fe to -ves)wife: wiveshero: heroes (some nouns ending in -o add -es, some do not)tomato: tomatoesman: men (words from various origin languages that inherited differing plural forms)child: childrenfoot: feettooth: teethmouse: micecrisis: crisesparenthesis: parenthesesfungus: fungiradius: radiiantenna: antennaelarva: larvaegymnasium: gymnasiadatum: dataThere are several more variations and most of the rules cited above have exceptions. Some of the plural forms inherited from other languages are now alternating with regular plural form, that both plural forms are accepted. If you are in doubt of a plural form, always consult a dictionary.
Some plural words ending in "o" are photos, pianos, casinos, and zoos.
Some words ending in o that form their plural by adding s only include: pianos, duos, solos, tacos.
Because there is no standard rule for words ending in -o.
There is no hard-and-fast rule with regard to forming the plural forms of nouns ending in O. Some nouns adopt the ending -es, such as heroes, tomatoes, potatoes. Other nouns (especially those with two ending vowels) simply adopt an S, such as cameos, patios. Others appear in both forms: zeros/zeros, volcano/volcanoes, tornados/tornadoes. (The -es in these three is the dominant usage.)
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.
There's not a good one. You just have to memorize the "oddball" words that take "es" as an ending. Most words ending in "o" will just take an "s" as the ending. Use a Study Deck - see the link - to memorize the other words. Here's another good link to show you some of the most common plural endings for "o" words, too.
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.
es, like echo- e choes that would be plural
Cello > cellosDisco > discosRadio > radiosPhoto > photosPatio > patios
potato - potatoes tomato - tomatoes hero - heroes zero - zeros halo - halos whacko - whackos cameo - cameos patio - patios oreo - oreos
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