26. Plural forms

2. If the singular noun ends in ‑s, -ss, -sh, -ch, -x, or -z, add ‑es to the end to make it plural.

eg., Bus - Buses

      Lunch - Lunches

      Tax - Taxes

3. In some cases, singular nouns ending in -s or -z, require that you double the -s or -z prior to adding the -es for pluralisation.

eg., Gas - Gasses

4.If the noun ends with ‑f or ‑fe, the f is often changed to ‑ve before adding the -s to form the plural version.

eg., Calf - Calves

       Wife - Wives

       Wilf - Wolves

Note: Exceptions are roof (roofs), belief (beliefs), chief (chiefs), and such.

5.If a singular noun ends in ‑y and the letter before the -y is a consonant, change the ending to ‑ies to make the noun plural.

eg., City - Cities

       Sky - Skies

       Lady - Ladies

       City - Cities

6.If the singular noun ends in -y and the letter before the -y is a vowel, simply add an -s to make it plural.

eg., Monkey - Monkeys

       Day - Days

       Ray - Rays

       Boy - Boys

7. If the singular noun ends in -o, add ‑es to make it plural.

eg., Potato – Potatoes

       Tomato – Tomatoes

Note: Exceptions include Photo (Photos), Piano (Pianos), and Halo (Halos). 

8.If the singular noun ends in ‑us, the plural ending is frequently ‑I.

eg., Cactus – Cacti

9. If the singular noun ends in ‑is, the plural ending is ‑es.

eg., Analysis – Analyses

        Ellipsis – Ellipses

10. If the singular noun ends in ‑on, the plural ending is ‑a.

eg., Phenomenon – Phenomena

       Criterion – Criteria