What is form of a noun or verb when it indicates only one?

The form of a noun or verb that indicates only one is called the singular form.

Here's a breakdown:

* Nouns:

* Singular: Refers to one person, place, thing, or idea. Examples: *cat, book, city, happiness*

* Plural: Refers to more than one. Examples: *cats, books, cities, happinesses*

* Verbs:

* Singular: Used with singular noun subjects. Examples: *The cat sleeps. The book is interesting.*

* Plural: Used with plural noun subjects. Examples: *The cats sleep. The books are interesting.*

Examples:

* Singular noun: *The dog barks.*

* Plural noun: *The dogs bark.*

* Singular verb: *The child plays in the park.*

* Plural verb: *The children play in the park.*

Let me know if you have any more questions!