Agreement with the noun
Personal pronouns must agree with the nouns they stand for in number, gender and person.
- John is a good student. He won a prize in mathematics.
- Alice sings well. She has a golden voice.
- The children went on a picnic. They had a nice time.
Note that here the pronouns he, she and they are of the same number, gender and person as the nouns John, Alice and children respectively.
Singular nouns connected by and
When two singular nouns are connected by and, but refer to the same person, the pronoun should be singular.
- My uncle and guardian has given his consent to my plan. (Here the nouns uncle and guardian refer to the same person.)
- The Secretary and Treasurer put his signature to the document.
When two singular nouns connected by and represent different individuals, the pronoun should be in the plural.
- My uncle and my guardian have given their consent to my plan.
- The Secretary and the treasurer were asked to settle their differences quickly.
Position of I
Good manners require that I should come last in expressions like, John, Peter and I, Harry and I, You and I etc.
- You and I can do this job together.
- Robert and I have planned to go to Delhi.
The rule is: the person addressed should come first, the person spoken of second and the speaker himself last.
They with singular reference
They/them/their is often used to refer to a singular indefinite person who has already been mentioned. This is particularly common after indefinite pronouns like a person, anybody/one, somebody/one, nobody/one, whoever, each, every, either, neither and no.
- If anybody calls take their name and address.
- Somebody left their umbrella behind yesterday. Will they come and collect it from the office?
- Nobody was late, were they?
This use of they/them/their is convenient when the sex of the person referred to is unknown.