Turkish is a highly agglutinative language and copulas are rendered as suffixes, albeit with a few exceptions.
An infinitive ermek appeared in ancient texts; its stem er- became the current i-.
[1] The word idir, a variation of imek indicates alethic modality, so is used for emphasis, or to prevent ambiguity.
A complete sentence is formed by the addition of a suffix to a noun or adjective as an instance of nonverbal person agreement, with the conjugate verb "imek" only implied.
[1] Öğretmen-i-mteacher-COP-1SGÖğretmen-i-mteacher-COP-1SGI am a/the teacherÖğretmen-si-nteacher-COP-2SGÖğretmen-si-nteacher-COP-2SGYou are a/the teacherÖğretmenteacherÖğretmenteacherHe/she/it is a/the teacherÖğretmen-i-zteacher-COP-1PLÖğretmen-i-zteacher-COP-1PLWe are (the) teachersÖğretmen-si-nizteacher-COP-2PLÖğretmen-si-nizteacher-COP-2PLYou [plural/formal] are (a/the) teacher(s)Öğretmen-lerteacher-PLÖğretmen-lerteacher-PLThey are (the) teachersAlethic past tense is indicated with idi, another variation of imek.