Nouns ending in o preceded by a consonant typically form their plural by adding -es, though some follow irregular patterns based on origin, pronunciation, or convention. These include words like hero, echo, and piano.
Most nouns ending in a consonant + o form their plural by adding -es. This rule applies to words derived from Latin or Italian, especially those with stressed final syllables. For example, "hero" becomes "heroes," "echo" becomes "echoes," and "potato" becomes "potatoes." The addition of -es preserves the vowel sound and avoids awkward pronunciation.
However, not all such nouns follow this pattern. Some retain the singular form in plural contexts due to established usage or phonetic ease. Words like "kangaroo," "mango," and "zoo" take -s despite ending in consonant + o. This variation arises from the influence of native English speech patterns and frequency of use. The plural "zoos" sounds smoother than "zooes," which is why the -s form dominates.
| Word | Plural Form | Rule Applied |
|---|---|---|
| hero | heroes | Add -es (consonant + o) |
| echo | echoes | Add -es (consonant + o) |
| piano | pianos | Add -s (common usage, no -es) |
| tomato | tomatoes | Add -es (regular pattern) |
| buffalo | buffaloes | Add -es (American English spelling) |
The distinction between -es and -s endings often hinges on pronunciation and historical borrowing. Words like "bureau," "cruet," and "papaya" reflect older French or Spanish roots, where the -es plural was preserved. But in modern American English, many of these have shifted toward -s due to simplification. For example, "bureaus" is still acceptable, but "bureaus" is more common than "bureaus" in formal writing.
A notable exception is "kangaroo." Despite ending in a consonant + o, its plural is "kangaroos," not "kangarooes." This follows the general tendency in English to favor -s over -es when the resulting word is easier to pronounce. The -es ending can create awkward stress patterns, particularly in rapid speech. The rule isn't purely linguistic-it's phonetic and social.
One non-obvious fact: the plural of "potato" is "potatoes," not "potatos." This is because the word entered English via Spanish "patata," which itself came from Taino. The -es ending reflects a historical pattern seen in many loanwords from Romance languages. Similarly, "volcano" becomes "volcanoes," not "volcanos," following the same logic. These are not arbitrary choices-they stem from consistent morphological rules applied during lexical adoption.
Consider the word "piano." It's borrowed from Italian, where pluralization uses -i. But in English, we don't apply Italian plural rules. Instead, we use -s. So "pianos" is standard. However, in musical contexts, you might hear "pianos" used to refer to multiple instruments, while "pianos" is used in everyday speech. This shows how context shapes usage.
I once observed a student writing "echoes" incorrectly as "echoes" in a high school essay. The teacher corrected it to "echoes," citing the rule: consonant + o → -es. The student later asked why "photos" is correct but "echoes" isn't. The answer lies in the word's origin. "Photo" comes from Greek "phōtos," and its plural is formed with -s. "Echo" comes from Greek "ēchos," and its plural follows the -es rule. Not all words ending in o behave the same way-even if they share a root.
Another common confusion is with "torpedo." Its plural is "torpedoes," not "torpedos." This is because the word entered English through Italian, where the plural is "torpedini." English adapted the -es form, preserving the original stress and sound. In contrast, "tornado" becomes "tornados" in American English, though "tornados" is less common in British English, where "tornadoes" prevails. Regional variation matters.
When in doubt, consult authoritative sources. The Oxford English Dictionary notes that plural formation for words ending in consonant + o depends on etymology and frequency of use. Merriam-Webster's Collegiate Dictionary confirms that most such words take -es, but exceptions exist based on phonetic ease and regional norms.