What is the function of an apostrophe when used before 's'?

The use of an apostrophe before an 's' primarily serves to indicate possession by a singular noun. This grammatical function allows us to show that something belongs to someone or something. For example, in the phrase "the dog's leash," the apostrophe-s signifies that the leash belongs to the dog.

This form of possession is essential in clarifying relationships between nouns and helps avoid ambiguity in writing. In English, when you want to express that one entity possesses or is associated with another, the apostrophe followed by 's' is the correct way to convey that idea.

This distinction becomes particularly important when discussing nouns in context where ownership or relationships need to be explicitly stated. For instance, saying "Sarah's book" tells us that the book is owned by Sarah, which is a direct use of the apostrophe to show possession.