The reflexive case of they, the third-person plural personal pronoun. The group of people, animals, or objects previously mentioned, as the object of a verb or following a preposition (also used for emphasis).
"The students cleaned up the classroom themselves after finishing their project."
This word is formed by combining the pronoun "them" with the reflexive suffix "-selves." It functions as a plural form of "themselves," referring back to the subject of the sentence.