Pronoun shifting is a common error, whereby the writer switches the pronoun number (such as from I to we) or the pronoun person (such as from one to you) within a given sentence. Therefore, pronouns must be used consistently.

       E.g. If someone loses his way in the airport, they can ask an employee for directions.

Singular pronoun “someone (and his)” switches to the plural pronoun “they”. Both pronouns refer to the subject (and thus to the same antecedent). Therefore, the plural pronoun “they” must be changed to the singular pronoun “he”.

              E.g. One cannot sleep soundly if you exercise vigorously before retiring to bed.

Pronoun “One” switches to “you” halfway through. To maintain consistency, the pronoun “you” must be changed to the pronoun “one”.