Writing Style

Use the plural form when you refer to more than one thing (noun).

• This week, several of our instructors were sick.
• Managing pain is one of the most important things that nurses must consider.
• There have been a lot of studies done on Type II diabetes in Qatar.

Rules

• Add -s to singular nouns (e.g., boat-boats, house-houses).
• Add -es to singular nouns ending in s, x, z, ch, and sh (e.g., bus-buses, box-boxes, batch-batches, wish-wishes ).
• Add -ies to singular nouns ending in y (e.g., penny-pennies, baby-babies).

Exceptions

• Irregular noun plural forms (e.g., woman-women, child-children, knife-knives).
• Some nouns have the same singular and the plural forms (e.g., sheep-sheep, species-species).
• Some nouns are count and non-count
• Use plural nouns with singular verbs (e.g., The news is not good. Linguistics is the study of language).
• Use plural nouns with plural verbs (e.g., Her scissors are sharp. Those reading glasses are mine).

More information

"The Noun", Robin L. Simmons.

"Plural Noun Forms", Guide to Grammar.