Ethnicity is a matter of self identification Language is only relevant to the extent that it influences people s self identification If people don t feel they re ethnically Iranian but only Persian or Kurdish or Ossete or whatever so that we have to rely on language then there s really no such thing as Iranian people and this article should be redirected to Iranian languages If Iranian is a real thing then language isn t critical So do Persians Parsis Tajiks Kurds and Ossetes think of themselves as being one people or part of a coherent group of peoples If so then Iranian is a real thing If not it s an invention of linguists or historians