thempronoun
American /ðɛm/ British /ðem/
people or thingsused as the object of a verb or preposition to refer to two or more people or things already mentioned or clear from context
any genderused as the object of a verb or preposition to refer to a single person whose sex is not stated or not known, or who is neither male nor female
This matches the singular use of the subject form they (see they, sense 2): if anyone calls, tell them I'll be back soon.
Word family
Usage
The singular use of them (sense 2) matches singular they; it is now the standard neutral choice both when a person's sex is unstated or unknown and for a person who identifies outside male and female.