Definitions:

1. 3rd person nominative singular gender-neutral pronoun, indicating a specific person without specifying a male or female gender, or indicating a person who is genderqueer; used with plural verbs pronoun
   • This is my housemate, Robin; they live on the 3rd floor.
2. 3rd person nominative singular pronoun, indicating a person who is hypothetical or whose identity is unknown; used with plural verbs pronoun
   • Please tell the person whose car is parked in front of the store that they need to move it.
3. the 3rd person nominative plural pronoun; can stand in for any 3rd person nominative plural noun pronoun
   • They brought their dogs to the park.