# Indo-Iranian languages
**Indo-Iranian languages** form a major branch of the Indo-European language family, spoken by more than a billion people chiefly in Afghanistan, Bangladesh, India, Iran, Nepal, Pakistan, and Sri Lanka.[1](https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/indo-iranian) The branch consists of three groups: Indo-Aryan (also called Indic), Iranian, and Nuristani, with the exact position of the [Nuristani languages](https://www.edgepedia.org/nuristani-languages) disputed.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) Scholars reconstruct the common ancestor of these languages, Proto-Indo-Iranian, chiefly from the earliest attested forms of Old Indic and Old Iranian, the Rigveda and the Old Avesta.[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/)
| Key fact | Detail |
|---|---|
| Branches | Indo-Aryan, Iranian, and Nuristani; Glottolog identifies 95 Iranian, 217 Indo-Aryan, and six Nuristani languages[4](https://scholarsbank.uoregon.edu//bitstreams/ff0e1ac6-4272-4b03-8eff-e10cd453126a/download) |
| Speakers | More than a billion, chiefly in South Asia and Iran; Iranian languages alone about 95 million[1](https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/indo-iranian) |
| Earliest attestation | Fifteenth century BCE, in the Hurrian state of Mitanni, through divine, throne, and personal names and hippological terms[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9) |
| Proto-language | Proto-Indo-Iranian, reconstructed mainly from the Rigveda and the Old Avesta[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/) |
| Split | Indo-Aryan and Iranian tribes separated about 2000 BCE; proto-Iranian was presumably spoken in Central Asia in the late 3rd to early 2nd millennium BCE[6](https://www.iranicaonline.org/articles/iran-vi1-earliest-evidence/) • [2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) |
| Position in Indo-European | A clearly defined primary branch; no other branch can be clearly shown to be its nearest relative[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9) |
| Major literary languages | Persian, Ossetic, Kurdish, Baluchi, and Pashto on the Iranian side[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) |
## The three branches
**Indo-Aryan** is one of the two big sub-branches, with languages today spoken mainly in [South Asia](https://www.edgepedia.org/south-asia). Modern descendants of proto-Indo-Aryan include Hindi, Gujarati, Urdu, and Bengali, as well as the [Dardic languages](https://www.edgepedia.org/dardic-languages) spoken in northwestern Pakistan, which some scholars include under the Indic classification.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) • [1](https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/indo-iranian) Sanskrit, the most important source for all modern Indic languages, has survived as a liturgical language in India.[1](https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/indo-iranian) Apart from the Mitanni material, Indo-Aryan is confined to southeastern Afghanistan and the [Indian subcontinent](https://www.edgepedia.org/indian-subcontinent), and the language of its oldest texts, the Rigveda, is slightly less archaic than the Mitanni variety.[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9)
**Iranian** languages descend from a proto-Iranian parent language, unattested by texts, spoken presumably in Central Asia in the late 3rd to early 2nd millennium BCE.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) In historical times they have been spoken over an area stretching from easternmost Chinese Turkestan (Xinjiang, in the case of Sogdian and Khotanese) to western Europe, where Alanic, a descendant of Scythian, was spoken in the Caucasus area.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) Because of this wide geographical distribution, Iranian is more diverse than Indo-Aryan; the validity of Iranian as a single sub-branch has even been doubted by some scholars.[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9) The Iranian languages are known from three chronological stages, Old, Middle, and New Iranian, and Persian is the only language of which all three stages are known, descending from [Old Persian](https://www.edgepedia.org/old-persian), the language of the Achaemenid empire (6th–4th centuries BCE), through Middle Persian, the language of the Sasanian empire (3rd–7th centuries CE).[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) Today the major literary [Iranian languages](https://www.edgepedia.org/iranian-languages) are Persian (Fārsi), spoken throughout Iran, Afghanistan, and [Tajikistan](https://www.edgepedia.org/tajikistan); Ossetic in the southern Caucasus; Kurdish; Baluchi; and Pashto.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/)
**Nuristani** languages, spoken in the mountains of eastern Afghanistan, appear to constitute a separate third branch of Indo-Iranian, but the exact relationship is disputed.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) Assessing their position is described as a difficult question in current subgrouping work.[7](https://www.cambridge.org/core/books/indoeuropean-language-family/introduction/F143855FAE64FB937D00ECC9A4A0A08C)
## Proto-Indo-Iranian and its reconstruction
Several important linguistic changes took place between Proto-Indo-European and Indo-Iranian.[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/) In the vowel system, the Proto-Indo-European triple series *ē, *ō and the corresponding diphthongs merged into a single series with *ā, and vocalic *n̥ and *m̥ became *a before this merger. The historical correspondences are partly obscured by other developments, such as Brugmann's Law, the change of *o to ā in open syllables.[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/)
In the consonant system, the Proto-Indo-European velar series were reduced: *k and *kʷ (with voiced and aspirated counterparts) merged, while the palatals *k̂, *ĝ, *ĝh became the palatal affricates *ć, *j, *j́h. A new phoneme *š, with its allophone *ž, developed from several sources, most famously through the so-called RUKI rule, by which *s became *š after the vowels i and u, after *r and *r̥, and after velars and labials.[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/) The RUKI rule continued to be active in Proto-Indo-Iranian and Old Indic.[8](https://ebrary.net/106990/economics/sound_changes)
Two special developments involving voiced aspirates are named laws. By Grassmann's Law, in a sequence of two aspirated consonants the first lost its aspiration, so that a reduplicated present *dha-dhā- became *dadhā- "to place." Bartholomae's Law holds that when a cluster of consonants began with a voiced aspirate, the aspiration shifted onto the cluster's final element, which was itself voiced, so that every member of the cluster came out voiced, as seen in *augh-ta > *aug-dha.[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/) Bartholomae's Law is active in Sanskrit and reflected in Old Avestan [morphophonology](https://www.edgepedia.org/morphophonology), so it must be reconstructed for Proto-Indo-Iranian and even Proto-Iranian; whether it is a Proto-Indo-European law or an Indo-Iranian innovation is disputed, since there are hardly any traces of it outside Indo-Iranian.[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9) Whether Grassmann's Law occurred already in Proto-Indo-Iranian or only later in Indo-Aryan is likewise difficult to determine, because Iranian and Nuristanic generally lost breathy voice.[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9)
The morphologies of Rigvedic and Old Avestan differ little and must have been fairly close to that of Proto-Indo-Iranian. Most of the Indo-Iranian grammatical categories, including number, gender, case, and tense, are found in other [Indo-European languages](https://www.edgepedia.org/indo-european-languages) as well, and dual forms survived in nouns, adjectives, pronouns, numerals, and verbs. The morphology is pervaded by the Indo-European ablaut system, the alternation of vowel grades in roots, suffixes, and endings.[3](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/)
## Position within Indo-European
There is no question that all Indo-Iranian languages are related to one another much more closely than to any other Indo-European language, so Indo-Iranian is clearly defined as a primary branch of Indo-European.[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9) Its relationship to the other branches is harder to describe: in the history of the field it has variously been grouped with quite distinct branches, and nearly every neighboring sub-branch except Tocharian has at some point been assumed to be its nearest relative. A 2022 assessment concludes that no other branch can be clearly shown to be the nearest relative of Indo-Iranian; agreements with other branches are mostly common archaisms, parallel developments, or part of an areal spread (features spread by language contact, not common descent).[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9) A possible subgroup consisting of Indo-Iranian and Balto-Slavic is occasionally discussed in the literature.[7](https://www.cambridge.org/core/books/indoeuropean-language-family/introduction/F143855FAE64FB937D00ECC9A4A0A08C)
Under the traditional classification, used until the early 20th century, Indo-European was divided into eastern satəm languages, including Balto-Slavic, Armenian, and Indo-Iranian, and western centum languages, such as Germanic, Celtic, Latin, and Greek, based on how the palatal velars *k̂, *ĝ, and *ĝh developed.[9](https://www.iranicaonline.org/articles/iran-vi4-language-origins/)
## Prehistory and dispersal
The Indo-Aryan and Iranian tribes separated about 2000 BCE, but attempts to correlate the proto-[Indo-Iranians](https://www.edgepedia.org/indo-iranians) with archaeological sites are all problematic.[6](https://www.iranicaonline.org/articles/iran-vi1-earliest-evidence/) The Indo-Iranian branch would have been spoken several millennia earlier somewhere, perhaps, in the area of southern Russia.[2](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/) One hypothesis holds that Indo-Aryan began as the southern branch, its speakers later spreading in western and eastern directions, perhaps pushed by [Iranian peoples](https://www.edgepedia.org/iranian-peoples) arriving out of the north, and it further pictures Iranian as stretching across a vast area from the Pontic steppe toward Central Asia and [Mesopotamia](https://www.edgepedia.org/mesopotamia).[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9)
The dialectal split between Indo-Aryan and Iranian has been argued to go back to the very emergence of Proto-Aryan (Proto-Indo-Iranian) from Late Proto-Indo-European, far from India and Iran.[10](https://doi.org/10.5871/bacad/9780197262856.003.0003) The spreading Indo-Iranian branch came into contact with the already-diverged branches of Uralic about 4,000 years ago, and loanwords borrowed into Uralic from Indo-Iranian donor languages have been a long-studied source of evidence, analyzed through the sound substitutions required by the very different phoneme systems of the two families.[11](https://www.annualreviews.org/content/journals/10.1146/annurev-linguistics-011619-030405)
The earliest written evidence for an Indo-Iranian variety is the fifteenth-century BCE Mitanni material in the Hurrian state of Mit(t)an(n)i and surrounding areas, consisting of divine, throne, and personal names and hippological (horse-training) terms; linguistically and culturally this variety seems to belong rather to Indo-Aryan.[5](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9)
## Study of the branch
Sir [William Jones](https://www.edgepedia.org/william-jones) and Friedrich Schlegel were the first to identify the Iranian family as a branch of Indo-European, and in 1786 Jones showed how Sanskrit, Latin, Greek, and the [Germanic languages](https://www.edgepedia.org/germanic-languages) are connected; as for Old Iranian, the French scholar Anquetil-Duperron brought the language to light when his 1771 translation of the Parsees' sacred text, the Avesta, appeared.[12](https://www.cambridge.org/core/books/abs/studies-on-the-iranian-world-before-islam/new-data-on-the-development-of-the-indoiranians-in-the-bronze-age/642253E0608738A8C60EE14D23D5BEA0) Brugmann's 1884 article saw only two cases where the recognized Indo-European branches might be grouped together, Indo-Iranian and Balto-Slavic, and since then the family has continued to be thought of in terms of the branches he identified.[13](https://www.cambridge.org/core/books/indoeuropean-language-family/methodology-in-linguistic-subgrouping/0397257B6912B8708F1AB073EF45B472)
Research on the branch remains active. A 2024 study revisited the interaction between regular sound change and later analogy in the development of the outcomes of Brugmann's Law in Indo-Iranian, defending the traditional purely phonological formulation against a revised, accent-sensitive version.[14](https://onlinelibrary.wiley.com/doi/10.1111/1467-968X.12272) A current research project at the Dahlem Center for Linguistics studies the languages of the so-called "Indo-Iranian Frontier" in present-day Afghanistan and Pakistan, combining field research and descriptive work with historical-comparative studies.[15](https://www.dcl.fu-berlin.de/en/projekte/projektliste/halfmann-indo-iranian/index.html)
## References
1. [Indo-Iranian, Encyclopedia.com](https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/indo-iranian)
2. [Prods Oktor Skjærvø, "IRAN vi. IRANIAN LANGUAGES AND SCRIPTS," Encyclopaedia Iranica (2006, updated 2018)](https://www.iranicaonline.org/articles/iran-vi-iranian-languages-and-scripts/)
3. [Prods Oktor Skjærvø, "IRAN vi. IRANIAN LANGUAGES AND SCRIPTS (5) Indo-Iranian," Encyclopaedia Iranica (2006, updated 2018)](https://www.iranicaonline.org/articles/iran-vi5-indo-iranian/)
4. [Patterns of Morphosyntactic and Functional Diversification, University of Oregon dissertation (2025)](https://scholarsbank.uoregon.edu//bitstreams/ff0e1ac6-4272-4b03-8eff-e10cd453126a/download)
5. [Martin Joachim Kümmel, "Indo-Iranian," in Thomas Olander (ed.), The Indo-European Language Family: A Phylogenetic Perspective, Cambridge University Press, 2022, pp. 246–268](https://www.cambridge.org/core/books/indoeuropean-language-family/indoiranian/C01D66B2DA24680E0808EFEC10E389C9)
6. [Prods Oktor Skjærvø, "IRAN vi. IRANIAN LANGUAGES AND SCRIPTS (1) Earliest Evidence," Encyclopaedia Iranica](https://www.iranicaonline.org/articles/iran-vi1-earliest-evidence/)
7. [Introduction, in The Indo-European Language Family, Cambridge University Press, 2022](https://www.cambridge.org/core/books/indoeuropean-language-family/introduction/F143855FAE64FB937D00ECC9A4A0A08C)
8. [Sound changes, Handbook of Comparative and Historical Indo-European Linguistics](https://ebrary.net/106990/economics/sound_changes)
9. [Prods Oktor Skjærvø, "IRAN vi. IRANIAN LANGUAGES AND SCRIPTS (4) Origins of the Iranian Languages," Encyclopaedia Iranica](https://www.iranicaonline.org/articles/iran-vi4-language-origins/)
10. [Asko Parpola, "From the dialects of Old Indo-Aryan to Proto-Indo-Aryan and Proto-Iranian," in Indo-Iranian Languages and Peoples, British Academy/Oxford Academic, 2003](https://doi.org/10.5871/bacad/9780197262856.003.0003)
11. [The Origin and Dispersal of Uralic: Distributional Typological View, Annual Review of Linguistics](https://www.annualreviews.org/content/journals/10.1146/annurev-linguistics-011619-030405)
12. [New Data on the Development of the Indo-Iranians in the Bronze Age, in Studies on the Iranian World: Before Islam, Cambridge University Press](https://www.cambridge.org/core/books/abs/studies-on-the-iranian-world-before-islam/new-data-on-the-development-of-the-indoiranians-in-the-bronze-age/642253E0608738A8C60EE14D23D5BEA0)
13. [James Clackson, "Methodology in Linguistic Subgrouping," in The Indo-European Language Family, Cambridge University Press, 2022](https://www.cambridge.org/core/books/indoeuropean-language-family/methodology-in-linguistic-subgrouping/0397257B6912B8708F1AB073EF45B472)
14. [Grestenberger (2024), "Sound Change and Analogy, Again: Brugmann's Law and the Hunt For O-Grades in Indo-Iranian," Transactions of the Philological Society](https://onlinelibrary.wiley.com/doi/10.1111/1467-968X.12272)
15. [The Linguistic (Pre-)History of the Indo-Iranian Frontier, Dahlem Center for Linguistics, Freie Universität Berlin](https://www.dcl.fu-berlin.de/en/projekte/projektliste/halfmann-indo-iranian/index.html)
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*Topic: Encyclopedia › Society and history › Languages and linguistics › Languages and dialects › Language families and classification › Named language families › Indo-European family*
*Initially written Sep 17, 2026 · Reviewed: Oct 25, 2026 · Edited: Oct 15, 2026; Oct 25, 2026 · Last review: Oct 25, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license