The demography of Iran is as diverse and complex as the geography. As of 2001, Iran was estimated to have 66,128,965 inhabitants, which would make it the sixteenth largest country in the world in terms of population. At first glance, this might suggest a fairly low density of population: Turkey, for example, has almost exactly the same number of people in a country half the size, giving it twice the population density of Iran (220 people per square mile as opposed to 103 in Iran). Indeed, the population density in Iran is about the same as that in Afghanistan, less than that in Iraq (135 per square mile), and a mere fraction of that in Pakistan (460 per square mile), Israel (732 per square mile), or Lebanon (902 per square mile). These statistics, however, are misleading unless one also takes into account another very important element in the geographical character of the country: over half of the land is made up of essentially uninhabitable mountains and deserts, so that the population is actually concentrated in a relatively small but diffuse area and is generally more dense in the north and west of the country.
All of this population is Iranian in the sense that the people are citizens of the nation-state of Iran. The population is also quite uniform in terms of religion: over 99 percent are followers of Islam, either Shi‘ite Muslims (estimates range from 89 to 95 percent) or Sunni Muslims (4 to 10 percent). Language, however, is also a powerful or determining factor in individual and group identity, and the population of Iran is anything but homogeneous in that regard. Over two-thirds of the people speak languages or dialects belonging to what is known as the Iranian branch of the Indo-European family of languages. The Iranian languages are thus closely related to some languages spoken in India and more distantly related to Romance, Germanic, or Slavic languages. The most widely spoken of the Iranian languages is Modern (or New) Persian, which is the offi cial and commonly understood language of the country. It is the mother-tongue, however, of only a slight majority of the population, and it is not mutually intelligible with other Iranian languages such as Kurdish or Baluchi. Turkic languages and dialects, which belong to the Ural-Altaic family and are unrelated to the Iranian languages, are spoken by some 26 percent of the population in Iran: by the now mostly sedentary and nontribal Azeri Turks, by the Qashqâi tribal confederation, and by the formerly nomadic or seminomadic tribes usually called Turkomans.
Some of these languages and dialects are only spoken and have no written form. The literary languages in Iran use the Arabic script, and they have been affected to varying degrees by Arabic vocabulary and even Arabic grammar. That is one reason foreigners sometimes assume that the languages are related, when in fact they belong to completely different language families. Arabic is a Semitic language, and only about 1 percent of the people in Iran are native speakers of Arabic, but the language is widely studied and understood due to its religious importance in Islam. It is only because of historical circumstances that languages like Persian or Azeri came to be written in Arabic script. Despite its widespread use, this script is really not well suited for writing Persian and is even less satisfactory for Turkic languages. Arabic has several consonants that do not occur in Persian or Turkish, and those languages have some consonants that do not occur in Arabic. The vowel structure in Arabic words is generally predictable since words are constructed according to standard forms, and the script has characters for only three long vowels (there are ways of indicating the short vowels, but these are not usually written). Turkish, on the other hand, has eight distinct vowels, and there are no rules for predicting what vowels will be used in Persian and Turkish words. The ambiguities in the script thus make learning to read those languages somewhat more difficult than might otherwise be the case.