By adding –es to nouns ending in -o.
| Singular | Plural | Singular | Plural | |
|---|---|---|---|---|
| buffalo* | buffaloes | potato | potatoes | |
| echo | echoes | tomato | tomatoes | |
| hero | heroes | torpedo | torpedoes | |
| mosquito | mosquitoes | veto | vetoes | |
| negro | negroes | volcano | volcanoes |
*The plural form of buffalo can also be buffalo .