One day the doctor asked the doctor's assistant for the doctor's calendar. Then the doctor checked the doctor's calendar to see what appointments the doctor had that day. Then the doctor returned the doctor's calendar to the doctor's assistant for the doctor's assistant to use to schedule the doctor's patients' appointments.
That doesn't sound like we normally speak. We use pronouns to replace nouns to avoid unnecessary repetition.
One day the doctor asked her assistant, James, to hand her the appointment calendar. Then she checked it to see how many appointments she had that day. After that, she returned the calendar to James and asked him to use it to schedule her other patients' appointments.
That sounds a lot better.
Definition: The prefix pro means for or in place of. Pronouns stand in for nouns or replace them. Personal pronouns replace nouns that refer to people or things.
Personal pronouns have
|1st person||I||we||me||us||my, mine||our, ours|
|2nd person||you||you||you||you||your, yours||your, yours|
|3rd person||he, she, it||they||him, her, it||them||his, her, hers, its||their, theirs|