For nouns ending in O
1. For some nouns ending in O, add -es to the end of the word.
domino - dominoes
hero - heroes
potato - potatoes
tomato - tomatoes
torpedo - torpedoes
2. For nouns ending in O that are short forms of words, add -s.
bio (from biography) - bios
photo (from photograph) - photos
piano (from pianoforte) - pianos
zoo (from zoological garden) - zoos
3. For other nouns ending in O, you can add -s or -es.
flamingo - flamingos or flamingoes
mango - mangos or mangoes
mosquito - mosquitos or mosquitoes
tornado - tornados or tornadoes
volcano - volcanos or volcanoes
zero - zeros or zeroes