When ‘they’ means ‘he or she’

In English, singular third person pronouns make a person’s gender explicit: If Mary calls, she can leave a message. If my brother calls, he may want to talk to me . Sometimes, we don’t know if the person we are talking about is male or female. To include both possibilities, we may say ‘he or she’: If someone calls and I’m not here, he or she can leave a message. He and she are singular pronouns, whereas they is the plural third person pronoun. However, we can use they to refer to just one person, to avoid saying ‘he or she’: If a customer calls and I’m not here, they can leave a message. The same happens with other third person pronouns and possessives: ...