In grammar, a possessive form refers to the grammatical form of a noun or pronoun that express a relationship of belonging. In the case of noun personal pronouns such as I, you, he, she, etc. there are fixed personal pronouns for each one such as mine, your, his or her. However, in the case of nouns, which are words that name people, animals or place and in the case indefinite pronouns the possessive form is commonly used by adding an apostrophe (’) and a letter "s", although this changes if the noun or pronoun ends in "s" or is plural. In the case of the noun, "someone" which refers to an indefinite individual and therefore is singular the possessive is formed by adding the apostrophe and the "s", which means the possessive form of the word someone is "someone's", for example in the sentence "This book should belong to someone" can be changed to "This should be someone's book" by using the possessive form of the word someone.
