Iranian V Persian
I see you asked about this on the Wiki Project Iran talkpage. Iranian, originally meant the Iranian peoples, which are a number of ethnic groups including the Persian people. The Iranian sate was named after the Iranian people and many dynasty's that ruled Iran historicly were not ethnically Persinal at all. Despite being known as Iran internally, for it's entire history, the Greeks refered to the country as Persia, in reference to the country's most important ethnic group at the time and this name was later adopted by the Roman's and then used throughotu the West until 1936 when Reza Shah got the Western states to officially recognise the country's name as Iran. Now although, in today's world "Iranian" most commonly refers to citizen of Iran and "Persian" to the ethnic group Persian people (not all of which are from Iran, since there are milions of ethnic Presians in Afghanistan, Tajikistan and Uzbekistan), with the term "Iranic" being commonly used to refer to the "Iranian Peoples" in the sense of all these different ethnic groups (Persians, Pashtuns, Kurds, Baluchis, ect.), however, due to wikipedia policies of English being Wikipedia's language here, Iran historicly is being refered to as the "Persian Empire" or "Persia" (which is infact a region in Iran), it's citizens as "Persians" (although many of the notable Iranian citizens of the past weren't ethnic Persians and infact none of the kings of the "Persian" empire from 1501 (re-establishment of Iranian state) until 1979 (abolishment of monarchy) were ethnic Persians) and so on wikipedia Iranian individuals prior to 1936 are refered to as Persians and Iran is refered to as Persia in articles concerning pre-1936 history.