
Originally Posted by
www.web.ask.com
Is it -os or -oes?
a. For most words that end in -o, simply add -s for the plural form. These include:
1) words of Spanish or Italian origin, especially those connected with music e.g. cello/cellos, piano/pianos, soprano/sopranos, concerto/concertos;
2) words where there is another vowel in front of the -o e.g. studio/studios, patio/patios, zoo/zoos, cuckoo/cuckoos, kangaroo/kangaroos
3) words that are abbreviations e.g. rhino/rhinos (rhino = rhinoceros), hippo/hippos (hippo = hippopotamus), kilo/kilos (kilo = kilogram), photo/photos (photo = photograph)
There are some exceptions.
A) Certain words ending in -o take -es for the plural form. These include: domino/dominoes, echo/echoes, hero/heroes, potato/potatoes, tomato/tomatoes
B) Certain words ending in -o can take either -es or -s. These include:
mango/mangoes (or mangos), mosquito/mosquitoes (or mosquitos), tornado/tornadoes (or tornados), volcano/volcanoes (or volcanos)