When we add -s or -es to nouns ending in -o, we create their plural forms. Here is a list of some common nouns ending in -o and the change that happens to them when they become plural. It is important to note that each word may have exceptions depending on its origin and common usage.
| Singular | Plural |
|---|---|
| banjo | banjos/banjoes |
| archipelago | archipelagos/archipelagoes |
| cargo | cargos/cargoes |
| desperado | desperados/desperadoes |
| halo | halos/haloes |
| lasso | lassos/lassoes |
| mango | mangos/mangoes |
| memento | mementos/mementoes |
| motto | mottos/mottoes |
| tornado | tornados/tornadoes |
| volcano | volcanos/volcanoes |
| zero | zeros/zeroes |
| avocado | avocados/avocadoes |
| domino | dominos/dominoes |
| grotto | grottos/grottoes |
| mosquito | mosquitos/mosquitoes |
| flamingo | flamingos/flamingoes |
| fresco | frescos/frescoes |
| ghetto | ghettos/ghettoes |
| torpedo | torpedos/torpedoes |
| veto | vetos/vetoes |
| embargo | embargos/embargoes |
| calico | calicos/calicoes |
| dado (carpentry) | dados/dadoes |
| gecko | geckos/geckoes |
| credo | credos/credoes |
| manifesto | manifestos/manifestoes |
| innuendo | innuendos/innuendoes |
| placebo | placebos/placeboes |
| solo | solos |
| piano | pianos |
| photo | photos |
| video | videos |
| radio | radios |
| studio | studios |
| ratio | ratios |
| zoo | zoos |
| cello | cellos |
| casino | casinos |
| cappuccino | cappuccinos |
| espresso | espressos |
| octavo | octavos |
| quarto | quartos |
| trio | trios |
| soprano | sopranos |
| alto | altos |
| kimono | kimonos |
| taco | tacos |
| nacho | nachos |
| burrito | burritos |
| avocado | avocados/avocadoes |
| calypso | calypsos |
| dynamo | dynamos |
| placebo | placebos/placeboes |
| lingo | lingos |
| logo | logos |
| memo | memos |
| metro | metros |
| micro | micros |
| pedalo | pedalos |
| polo | polos |
| portico | porticos |
| portfolio | portfolios |
| potato | potatoes |
| tomato | tomatoes |
| echo | echoes |
| hero | heroes |
| buffalo | buffalo/buffaloes/buffalos |
| tornado | tornados/tornadoes |
| volcano | volcanos/volcanoes |
| armadillo | armadillos |
| piano | pianos |
| photo | photos |
| pro | pros |
| psycho | psychos |
| raviolo (culinary; rare in English) | ravioli (as collective) / raviolos |
| scenario | scenarios |
| studio | studios |
| tattoo | tattoos |
| torero | toreros |
| tyro | tyros |
| weirdo | weirdos |
Words ending in -o form their plural in -os or -oes. Generally, those which have a vowel before the final -o simply take -s (e.g. videos, audios). Most words that have a consonant before the final -o add -es (e.g. heroes, potatoes). However, there are exceptions, and usage can change over time or vary between different varieties of English.
