Nouns

Irregular plural nouns:
1. phenomenon: phenomena (existing thing; ~ hiện tượng)
- Gravity is a natural phenomenon.
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Male/Female:
1. waiter/waitress
2. actor/actress
3. heir/heiress
4. elector/electress
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Subject + Verb.
Singular/Plural agreements:
* singular or plural verbs? (http://wps.ablongman.com)
* singular or plural? (tolearnenglish.com)
- trousers, pants