The term Iran derives directly from Middle Persian Ērān, first attested in a third-century inscription at Rustam Relief, with the accompanying Parthian inscription using the term Aryān, in reference to the Iranians. The Middle Iranian ērān and aryān are oblique plural forms of gentilic nouns ēr- (Middle Persian) and ary- (Parthian), both deriving from Proto-Iranian *arya- (meaning "Aryan", i.e. "of the Iranians"), recognized as a derivative of Proto-Indo-European *ar-yo-, meaning "one who assembles (skilfully)". In the Iranian languages, the gentilic is attested as a self-identifier, included in ancient inscriptions and the literature of the Avesta,[b] and remains also in other Iranian ethnic names Alan (Ossetian: Ир Ir) and Iron (Ирон).
Historically, Iran has been referred to as Persia by the West, due mainly to the writings of Greek historians who referred to all of Iran as Persís (Ancient Greek: Περσίς; from Old Persian 𐎱𐎠𐎼𐎿 Pārsa), meaning "land of the Persians", while Persis itself was one of the provinces of ancient Iran that is today defined as Fars. As the most extensive interaction the Ancient Greeks had with any outsider was with the Persians, the term persisted, even long after the Greco-Persian Wars (499–449 BC).
In 1935, Reza Shah requested the international community to refer to the country by its native name, Iran, effective March 22 that year. As The New York Times explained at the time, "At the suggestion of the Persian Legation in Berlin, the Tehran government, on the Persian New Year, Nowruz, March 21, 1935, substituted Iran for Persia as the official name of the country." Opposition to the name change led to the reversal of the decision, and Professor Ehsan Yarshater, editor of Encyclopædia Iranica, propagated a move to use Persia and Iran interchangeably. Today, both Iran and Persia are used in cultural contexts, while Iran remains irreplaceable in official state contexts.
Historical and cultural usage of the word Iran is not restricted to the modern state proper. "Greater Iran" (Irānzamīn or Irān e Bozorg) refers to territories of the Iranian cultural and linguistic zones. In addition to modern Iran, it includes portions of the Caucasus, Anatolia, Mesopotamia, Afghanistan, and Central Asia.
The Persian pronunciation of Iran is [ʔiːˈɾɒːn]. Common Commonwealth English pronunciations of Iran are listed in the Oxford English Dictionary as / and /, while American English dictionaries such as Merriam-Webster's provide pronunciations which map to /, or likewise in Random House Webster's Unabridged Dictionary as /. The Cambridge Dictionary lists / as the British pronunciation and / as the American pronunciation. Similarly, Glasgow-based Collins English Dictionary provides both English English and American English pronunciations. The pronunciation guide from Voice of America also provides /.
The American English pronunciation / RAN may be heard in U.S. media. Max Fisher in The Washington Post prescribed / for Iran, while proscribing /. The American Heritage Dictionary of the English Language, in the dictionary's 2014 Usage Ballot, addressed the topic of the pronunciations of Iran and Iraq. According to this survey, the pronunciations / and / were deemed almost equally acceptable, while / was preferred by most panelists participating in the ballot. With regard to the / pronunciation, more than 70% of the panelists deemed it unacceptable. Among the reasons given by those panelists were that / has "hawkish connotations" and sounds "angrier", "xenophobic", "ignorant", and "not...cosmopolitan". The / pronunciation remains standard and acceptable, reflected in the entry for Iran in the American Heritage Dictionary itself, as well as in each of the other major dictionaries of American English.