Personal pronouns replace or refer to specific nouns, especially nouns referring to the people or objects involved in the sentence. Common personal pronouns include I, you, her, its, and they.
We heated the samples and measured their change in weight over five seconds.[We is the subject of the sentence; their refers to the noun samples.]
Choose a pronoun that matches the number and gender of the noun it refers to. Make sure that no other nouns with the same number and gender come between your pronoun and its antecedent. See Pronoun Reference.
Choose the form of the pronoun that is appropriate for its role in the sentence. See Pronoun Case.