A pronoun must agree with its antecedent, the noun it replaces, in person, gender, and number. "Maria lost her keys" is right because her is third person, feminine, and singular, just like Maria.
A pronoun is a word that replaces a noun or a noun phrase. Every pronoun needs an antecedent: the word that the pronoun stands for. The rule that a pronoun must match its antecedent in person, gender, and number is called pronoun agreement. It works much like subject-verb agreement, where the verb has to match its subject.
A pronoun is not an adjective. To learn more about the difference between the two, read the differences between pronouns and adjectives.
For learners of English as a second language (ESL), pronoun agreement can be a challenge. To make it clearer, here is a closer look at person, gender, and number agreement.
Person agreement
When you talk about yourself, use the first person: I, me, we, or us. When you talk to someone, use the second person: you. When you talk about someone or something else, use the third person: he, she, it, him, her, they, or them.
- My name is Beatrice, and I am the keeper of the secret library.
In this example, the pronoun I refers to Beatrice. Here are two more examples:
- A mysterious dog bit the kids, so they became ill.
- A mysterious dog bit the kids, and then it just disappeared.
Gender agreement
When you talk about a man or a boy, use he, him, and his. When you talk about a woman or a girl, use she and her. For example:
- Johnny forgot his lunch, and his friends gave him some money when he mentioned it.
- Sarah wants to talk to the manager, and she won't leave until her complaint is heard.
What if you do not know the person's gender? In conversation, people usually use they and their:
- If I catch the person who broke my car, they will feel my wrath.
In writing, this singular they is now accepted by major style guides and dictionaries. The verb stays plural, as in "they are" and "they were". You can also write he or she:
- If I catch the person who broke my car, he or she will feel my wrath.
He or she is correct, but it quickly becomes clumsy when a sentence or a paragraph needs it more than once. Many writers then use singular they, or rewrite the sentence in the plural: "If I catch the people who broke my car, they will feel my wrath." Using he for everyone, which older grammar books recommended, is now widely seen as outdated.
Number agreement
Use singular pronouns to replace singular nouns, and plural pronouns to replace plural nouns.
- Michael and Jordan do well at school because they study hard. (a plural pronoun for two people)
- Kevin cried when he was left home alone. (a singular pronoun for one person)
- The factory baked a thousand chocolate cookies, and Cookie Monster ate them all. (a plural pronoun for many things)
- This is my cookie, and it is delicious. (a singular pronoun for one thing)
Singular indefinite pronouns
The examples above are straightforward, and most learners understand them quickly. Indefinite pronouns are harder.
These indefinite pronouns are singular: somebody, someone, something, nobody, no one, nothing, anybody, anyone, anything, everybody, everyone, everything, each, either, and neither. They take a singular verb: "Everyone is here", not "Everyone are here."
But which pronoun refers back to them? Traditional grammar asks for a singular one, he or she. Today, singular they is the usual choice, both in speech and in most writing:
- Somebody left their bag on the subway.
- Everyone must pick up their own trash.
When you know the gender of the group, use the matching pronoun: "Each of the girls brought her own lunch." For more about the different kinds of pronouns, see what you need to know about pronouns.