The Mordvinic languages, alternatively Mordvin languages, or Mordvinian languages,
are a subgroup of the Uralic languages

Uralic languages

The Uralic languages constitute a language family of some three dozen languages spoken by approximately 25 million people. The healthiest Uralic languages in terms of the number of native speakers are Hungarian, Finnish, Estonian, Mari and Udmurt...

, comprising the closely related Erzya language

Erzya language

The Erzya language is spoken by about 500,000 people in the northern and eastern and north-western parts of the Republic of Mordovia and adjacent regions of Nizhniy Novgorod, Chuvashia, Penza, Samara, Saratov, Orenburg, Ulyanovsk, Tatarstan and Bashkortostan in Russia...

 and Moksha language

Moksha language

The Moksha language is a member of the Finno-Volgaic subdivision of the Uralic languages with about 500,000 native speakers. Moksha is the majority language in the western part of Mordovia....

.
Previously considered a single "Mordvin language",
it is now treated as a small language family. Due to differences in phonology

Phonology

Phonology is, broadly speaking, the subdiscipline of linguistics concerned with the sounds of language. That is, it is the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use...

, lexicon

Lexicon

In linguistics, the lexicon of a language is its vocabulary, including its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek "λεξικόν" , neut...

, and grammar

Grammar

In linguistics, grammar is the set of structural rules that govern the composition of clauses, phrases, and words in any given natural language. The term refers also to the study of such rules, and this field includes morphology, syntax, and phonology, often complemented by phonetics, semantics,...

, Erzya and Moksha are not mutually intelligible, to the extent that Russian language is often used for intergroup communications.

The two Mordvinic languages also have separate literary forms. The Erzya literary language

Literary language

A literary language is a register of a language that is used in literary writing. This may also include liturgical writing. The difference between literary and non-literary forms is more marked in some languages than in others...

 was created in 1922 and the Mokshan in 1923.

Phonological differences between the two languages include:

• Moksha retains a distinction between the vowels /ɛ, e/ while in Erzya, both have merged as /e/.
• In unstressed syllables, Erzya features vowel harmony
  Vowel harmony
  Vowel harmony is a type of long-distance assimilatory phonological process involving vowels that occurs in some languages. In languages with vowel harmony, there are constraints on which vowels may be found near each other....
  
   like many other Uralic languages, using [e] in front-vocalic words and [o] in back-vocalic words. Moksha has a simple schwa
  Schwa
  In linguistics, specifically phonetics and phonology, schwa can mean the following:*An unstressed and toneless neutral vowel sound in some languages, often but not necessarily a mid-central vowel...
  
   [ə] in their place.
• Word-initially, Erzya has a postalveolar affricate /tʃ/ corresponding to a fricative /ʃ/ in Moksha.
• Next to voiceless consonants, liquids
  Liquid consonant
  In phonetics, liquids or liquid consonants are a class of consonants consisting of lateral consonants together with rhotics.-Description:...
  
   /r, rʲ, l, lʲ/ and the semivowel
  Semivowel
  In phonetics and phonology, a semivowel is a sound, such as English or , that is phonetically similar to a vowel sound but functions as the syllable boundary rather than as the nucleus of a syllable.-Classification:...
  
   /j/ are devoiced in Moksha to [r̥ r̥ʲ l̥ l̥ʲ ȷ̊].

The medieval Muromian language may have been Mordvinic, or close to Mordvinic.