What type of noun requires the addition of an apostrophe and 's' to form its possessive?

The addition of an apostrophe and 's' to form the possessive is typically used for singular nouns. This construction indicates that something belongs to or is associated with a singular noun. For example, in the phrase "the dog's leash," the apostrophe and 's' signify that the leash belongs to one dog.

While plural nouns can also form possessives, the mechanics differ; plural nouns that do not end in 's' will still require an apostrophe and 's' (e.g., "children's toys"), while plural nouns that do end in 's' simply take an apostrophe after the existing 's' (e.g., "dogs' park"). Common nouns can take either form, and collective nouns can be singular or plural depending on context, but the direct relationship to possessive formation under discussion is primarily seen in singular nouns. Therefore, the requirement for using an apostrophe and 's' for possessives dominates in singular forms.