Luri and Bakhtiari, languages in the southwest part of Iran, are closer to Dari than to Farsi spoken in Tehran.
Bakhtiaris originate from Parthians.
Zoarastrians in Iran such as Yazd speak with a Dari dialect.
Dari has more Parthians words than Farsi.
Standard Farsi from Tehran is has been influenced by Azeri Turks who do not understand the Persian culture. So many cultural nuances in Farsi has been lost. On the contrary Dari has kept cultural nuances in its Dari language form.
Dari is the language of Khorasan. Farsi is the language developed by Azeri Turk Qajar dynasty in 19 century in Tehran.
Tajik in Tajikstan speak also Dari with some minor differences.
Ferdowsi wrote Shahnameh in Dari language.
Posted by Nick:
Tajik is the word referred to natives of Turkistan, Samarkand/Bokhara. In reality they are Turkic people, even today if you travel to Uzbekistan or Tajikistan, you will witness the Turkic looks speaking Turkic version of Farsi, in old days known as Bokhari which was always the courtly language Amirulabokhara (Turkistan). However we are not sure about their ancestors, according to Iranica Tajiks are the remains of Persian people. Ie During the Archemanid empire. According to Genetics and modern Science they are Mongolide/Turkic people, not different from Hazaras. The fact many regions of Tajikistan such as Qaria Afghan, and Badakhshan is a prove that Afghans also existed in the south of Turkistan, also Afghan qwami empires such as Saka/Abdaliates/Kushans/Pakhtrians etc show Afghan mixture. That's why some Tajiks look like Afghans. But that's one out of 30.
Gula Jan Wrehkmin has given you a hint. Tajiks who for years have been mixed ie Arabs of Bokhara which was their first city of light in the East, and Persians who found the gold mines that was discovered by Afghan sakas, but originally it can be considered the land of Altaics. Tajiks makeup less then 5% of Afghanistan mainly in the north who were immigrants recorded to have come into Afghanistan first time during Russian invasion of Turkistan, and the second one is during 1990s when Turkic were fighting among promoted by Russians, after Russian who lost everything after war with Afghans tried at best to not leave their colonials at peace, some 1 or 2 million Tajiks today lives in Afghanistan. However law passing in 2001 they have been given Afghan passport, although they shouldn't of get any since their nation Tajikistan didn't help Afghan refugees when they were at need so why would Turkics get Passports? Anyways that's a different political issue.
However if you are to Afghan Farsiwans like us, and yes we were always Afghan. From record of sanskrit to Awesta, and from latest Chinese source, to persian, and Arabs ie Al-Biruni born in Turkistan, all the sources from many sources makes it clear that nation of Afghans ranges from mother of cities "Balkh" to Takhti Sulyman "Sulyman mountains" today's balochistan also known as "Markan", and from Aravai "Herat" to Kabul. The word "Tajik" has never been used by us or any of us until Russians who after coming in connects with Turkics. Assumed any-one speaking a language similar to their Turkstan was classified as one people including people of Iran. Which was a misunderstanding. Russians being a socialism regime classified people not by their culture, looks or religions but only language. Once for those who doesn't know know much about Russian society will know what i am talking about. However the word "Tajik" was then reaching Europe ie France, and by 60s soon in English books and by 70s into America. However often got into usage during 1990s. Now it has become as an single ethnic group. Which is wrong, but hey Afghans made any reactions to stop usage after all where is the government to speak for it? Do Afghans have voice? no? I have the source in both Russian and English. Its very clear that it does not apply to Heratis, us Samaliwals, or Mazaris. So people should educated themselves in learning the word.
However it was assume by people that Tajiks may have come from the word "Crown" Taj which is an Awestian word lol Right its silly claim, the word "Taj" has used by every poet, Taj-e-Mahmud, Taj-e-Arsalan Taj-e etc etc etc etc and i have come across dozen times, even my cousin wears one LOL.
Just to let you let you know I have never seen a Tajik with blue eyes with both parents being Turkic, its always one side Russian or something, came across few here and there, then its normal since south of Tajikistan is an Afghan land ie known part of Badakhshan, therefore hindukush may have influence.
Tajik is Russian supported word that has been applied to any race speaking a same language. Including Iran as being labeled as "Tajik" but that was not the case, yet Russian society themselves look at from more socialistic point of view. This was never supported outside Soviet union, the bases of communism and their teaching followed this idea which again Afghanistan fall into the trap.
The word "Tajik" should only apply to Turkic people of Farsi speakers, although many assumed Tajiks are remains of Persian/Aryan origin but that's not supportive and in fact no such Civilization of Samarkand and Bukhara supported such people until coming of Afghan Sakas, Persian Archeamanids, Such assumptions were made without look at the local population, and consider the large number of Arabs and their outcome and then the Mongolian destruction which is well documented that 80% of Central Asia was disappearded right six feet under ground. Therefore it can reasonably said that only 15% of central Asians maybe native and the rest i guess considered "outsiders".