Words ending in -o form plural by adding '-s'. In some resources I have read some of these words needs '-es' to make plural (e.g. echo, buffalo). However it seems both form of all such words (-s or -es) are recorded in dictionaries. So is it correct to form plural form of all o-ending word by only adding '-s'?

  • The only one I can think of is the letter O, whose plural requires an apostrophe s: O's.
    – Jim
    Commented Sep 20, 2014 at 6:09
  • 3
    plurals of words ending in o - slideshare
    – Mina
    Commented Sep 20, 2014 at 7:43
  • 1
    @Jim Plurals "requiring an apostrophe?" What do you mean? Reading that I can't help hearing Lynne Truss at the back of my mind... "The only illiteracy with apostrophes that stirs any sympathy in me is the greengrocer's variety."
    – None
    Commented Sep 20, 2014 at 8:10
  • 1
    @Laure From CGEL, p.1586: "Plurals with 's: An apostrophe may be used to separate the plural suffix from the base with letters, numbers (notably dates), symbols, abbreviations, and words used metalinguistically: (i) p's and q's, 1960's, &'s, Ph.D.'s, if's and but's (ii) She got four A's and two B's. This practice is less common than it used to be; with dates and abbreviations ending in an upper case letter, the form without the apostrophe is now more usual: in the 1960s, two candidates with Ph.D.s."
    – user230
    Commented Sep 20, 2014 at 8:15
  • 1
    @Mina An excellent link! It would make a great source for anyone who wanted to write an answer.
    – user230
    Commented Sep 21, 2014 at 8:15

2 Answers 2


There is some good guidance given by Oxford Dictionaries (OUP) here showing quite a number of examples.

The basic guidance is

Nouns ending in -o can add either -s or -es in the plural, and some can be spelled either way.

As a general rule, most nouns ending in -o add -s to make the plural:

Those which have a vowel before the final -o always just add -s:

a list of the most common nouns ending in -o that are always spelled with -es in the plural:

singular    plural
buffalo     buffaloes
domino      dominoes
echo        echoes
embargo     embargoes
hero        heroes
mosquito    mosquitoes
potato      potatoes
tomato      tomatoes
torpedo     torpedoes
veto        vetoes

some of the common nouns ending in -o that can be spelled with either -s or -es in the plural:

singular      plural
banjo         banjos or banjoes
cargo         cargos or cargoes
flamingo      flamingos or flamingoes
fresco        frescos or frescoes

So there are some that 'require' the -es although there isn't a hard and fast 'rule' that you can apply.

Consider zero and hero; indistinguishable in their form and yet zeros is the standard plural of zero while heroes is the standard plural of hero.

"Plurals of nouns". Oxford Dictionaries. Oxford University Press. http://www.oxforddictionaries.com/words/plurals-of-nouns (accessed September 21, 2014).

  • As I said in the question actually most of listed form are correct in both form. Commented Sep 21, 2014 at 11:05
  • @PHPst I think what Oxford Dictionaries are suggesting is that 'echos', 'heros', 'potatos', etc. are 'wrong' in whatever sense OD class them as wrong - perhaps 'wrong' means extremely uncommon in modern writing.
    – Frank
    Commented Sep 21, 2014 at 11:27
  • Please limit your answer to a list of such words ( 'echos', 'heros',… ) so I can mark your answer as accepted. The Mina's link also contain some of these words. Thanks. Commented Sep 21, 2014 at 12:54
  • 1
    see also my favorite unclear plural: english.stackexchange.com/questions/134628/plural-for-photo Commented Sep 22, 2014 at 21:07
  • "zeros" is the standard plural? You learn something new each day... Anyway, it seems that the "safe bet" is actually to always add -es. Commented Oct 13, 2014 at 9:20

Acording to this excellent presentaion, there are only a few words that must be pluriezed using only -es. Here is a list of such words:

  • potato
  • tomato
  • echo
  • hero
  • veto
  • embargo
  • torpedo

(feel free to add any missing word to the list)

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .