Phoneme inventory (vowels, consonants)   •   Hard and soft consonants   •   Phonotactics  
Morphophonemic alternations   •   Palatalisation   •   Iotation   •   O > E   •   Y > I/E   •   Ě > I   •   Fleeting o/e
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Phoneme inventory (Zvukosbor)

Interslavic is neither a national language, nor does it try to emulate one. Instead, it is based on twelve national languages, each of them having its own phonology and its own corresponding orthography, tailored to fit its particular characteristics. In general, it can be said that the further South you go, the smaller the phoneme (sound) inventory becomes. Both spoken and written Interslavic should be in the very middle of them as much as possible.

A high number of phonemes makes intuitive writing and pronouncing Interslavic harder for those who are used to little phonemes. A low number, on the other hand, makes it harder to link a particular character or sound to a phoneme in his one's own language, and therefore has a negative effect on intelligibility. For example, the ideal pronunciation of the word for „five” would be something like [pjætʲ]. If we write this as pęť, a Russian can easily recognise his own pjať, a Serb his own pet and a Pole his own pięć; but for a Serb, there is no way of knowing when his own e and t become ę and ť without consulting a dictionary. On the other hand, in a simplified scheme pet could also be misunderstood as Russian peť „to sing” or Polish pet „cigarette butt”. In short: the easier we make it for the speaker/writer, the harder it becomes for the listener/reader, and vice versa.

To solve this dilemma, Interslavic has a basic set of phonemes that are present in all or a vast majority of the Slavic languages, more or less with the same phonetic values. In addition, Interslavic also has a set of optional phonemes that link directly to Old Church Slavonic and refer to particular phonetic differences between languages. Using the aforementioned word pęť as an example, Russian [pjætʲ] and South Slavic [pɛt] are two ways of pronouncing the very same word: the phonemes ę and ť indicate that their pronunciation varies among languages. These additional phonemes can be written by means of an additional set of optional letters, called „Naučny Medžuslovjansky”.

The following charts give an overview of phonemes in Interslavic, based on their most average pronunciation. The basic phonemes are shown in black, optional variations in gray.


Basic Interslavic has 7 vowel phonemes, five of which (a e i o u) have a rather uniform pronunciation, while the remaining two (ě y) have a pronunciation that may differ between speakers.

In addition, there are 4 optional vowels (å ę ò ų) whose pronunciation may vary. The diacritical marks are usually not written. In flavourised versions of Interslavic however, å can be written and pronounced as o, ę as ja, ò as e and y as i.

Front Near- front Central Near- back Back
i [i]
u [u]
ų [ow]
y [ɪ]
ò [ə]
e [ɛ] ě [jɛ]
o [ɔ]
ę [jæ]
a [a]
å [ɒ]

Interslavic also has syllabic r and ŕ (the latter belonging to the non-mandatory set). This is the case when it is preceded by a consonant and not followed by a vowel. It is pronounced with a schwa before it: trg [tərg], mŕtvy [mərtvɪ], cukr [ʦukər].


There are 24 basic consonants (including 3 affricates and 3 palatalised alveolars) with a more or less fixed pronunciation, and 6 optional consonants with a variable pronunciation:

Voiceles stops p [p] t [t] ť [tʲ] ~ [c]k [k]
Voiced stops b [b] d [d] ď [dʲ] ~ [ɟ]g [g]
Voiceless fricativesf [f] s [s] ś [sʲ] ~ [ɕ]š [ʃ] ~ [ʂ]h [x]
Voiced fricatives v [v] z [z] ź [zʲ] ~ [ʑ]ž [ʒ] ~ [ʐ]
Voiceless affricates c [ʦ] ć [ʨ]č [ʧ] ~ [ʈʂ]
Voiced affricates đ [ʥ] [ʤ] ~ [ɖʐ]
Nasals m [m] n [n] nj [nʲ] ~ [ɲ]
Trills r [r] rj [rʲ] ~ [r̝]
Laterals l [ɫ] ~ [l]lj [l] ~ [ʎ]
Approximants j [j]

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Hard and soft consonants (Tvrde i mekke suglasky)

Like all Slavic languages, Interslavic distinguishes between hard and soft consonants:

Softening is the process of adding [ʲ] to a consonant, resulting in a more palatal pronunciation. The number of soft equivalents of hard consonants in the phoneme inventory varies greatly from one language to another. In Interslavic only lj, nj and rj are mandatory, Scientific Interslavic also has ť ď ś ź (normally written t d s z). Their Cyrillic equivalents are ль нь рь and ть дь cь зь respectively (the ь, nowadays used as a softener, used to be a vowel in the old days: an ultrashort ĭ).

As can be seen from the table above, pronunciation of soft consonants varies. East Slavic speakers are likely to pronounce them as softened dental or alveolar consonants, West Slavic speakers rather as palatal consonants. Both pronuciations are equally correct.

The soft consonants also include postalveolar š, ž, č and , as well as the affricates ć and đ. The latter two are usually written and pronounced like č and ; the difference is of an etymological nature: ć and đ are the iotated counterparts of t and d (see below).

Before i, ě, ę and ŕ, a hard consonant can be softened or palatalised. That is why a word like buditi is pronounced either [budʲitʲi], [buɟici] or [buditi].

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Phonotactics (Fonotaktika)

Interslavic orthography is based on etymology and not on pronunciation, so that consonant clusters can arise that may appear inpronouncable for English speakers, for example vozvršenje. The only limitations are related to combining certain vowels with certain consonants.

It is important to know the following:

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Morphophonemic alternations (Morfofonemične alternacije)

Inflection is kept as regular as possible. However, alternations like palatalisation and iotisation of consonants are an omnipresent phenomenon in Slavic. They play a crucial role in both inflection and the world building process, and thus cannot be avoided even in the most simplified form of Interslavic – at least, if we want to avoid forms that come across as heavily artificial and unnatural.


Palatalisation means that under certain conditions the velar consonants k g h (as well as the dental affricatve c) are changed to the postalveolar consonants č ž š. This happens in the following cases:

Apart from the aforementioned vocative, palatalisation never occurs in the declension of nouns, adjectives and pronouns. Thus: sg. Čeh „Czech” > pl. Čehi „Czechs”; sg. dolgy „long” > pl. dolgi (animate) or dolge (inanimate).


A different thing happens when a hard consonant is followed by j. The result is called iotation, which is not the same thing as softening. The patterns according to which consonants interact with this j vary from one language to another. Sometimes, the result is the same as in the case of a softened consonant, sometimes it is different:

Iotation occurs mostly in -i- class verbs:

Iotation does not occur when a word with initial j is preceded by a prefix: s+jesti becomes sjesti, not *šesti.

Palatalisation + iotation

When a soft consonant is followed by j, both the consonant and the glide remain untouched. Any changes are blocked by the softener, so to speak. In scientific orthography ljj, njj etc. are represented as follows: ľj ńj ŕj ťj ďj śj źj šj žj čj. To prevent texts from becoming unnecessarily heavy on diacritics as well as for the ease of writing, we simply write lj nj rj tj dj sj zj šj žj čj in these cases. If the stem ends in -j, the following j- is simply swallowed: dvojiti > dvoj-ju > dvoju.

This occurs in the following situations:

Complicated as this may seem, all this means in writing is that the suffixes -je, -ji and the ending -ju do not cause iotation, but only palatalisation of k g h c.


The differences between softened, patalalised and iotated consonants are demonstrated in the following table (again, phonemes in gray are optional):

Hard pbfvmsztdrnlc kgh
Soft (’) śźťď rjnjljčžšj
Hard + j pjbjfjvjmjšžč (ć)(đ)
Cons. + ’ + j sj (śj)zj (źj) tj (ťj)dj (ďj) rj (ŕj)nj (ńj) lj (ľj)čjžjšj

The same goes also for combinations:

Hard stzdskzg
Soft (’)
Hard + j šč (šć)ždž (žđ)ščždž
Cons. + ’ + j stj (sťj)zdj (zďj)ščjždžj

O > E

Old Slavic used to have a peculiar intolerance of o following a soft consonant, and whenever such a sequence occurred because of an ending or a suffix, the o was changed to e. This development has left its marks in all Slavic languages, although nowadays they differ as to the degree in which the o/e rule is still applied. For example, in Russian soft consonant + o sequences are a rarity, while Polish has only some lexicalised remnants of the rule (f.ex. królewski „royal”, but: królowa „queen”).

This rule applies in Interslavic as well. Thus, endings like -o, -ov, -om, -ogo and -oj become -e, -ev, -em, -ego and -ej after a soft consonant. Because of the o/e rule, we have morje versus okno, krajev versus gradov, and čego versus kogo.

For reasons of transparency, suffixes are better left intact, though: svěžo, nočovati.

Y > I/E

In South Slavic and Ukrainian, as well as in spoken Czech and Slovak, i and y have merged into one vowel. In Interslavic, the pronunciation of y may therefore be [i], [ɪ], [ɨ] or anything in between. What matters, though, is that y can only occur after a hard consonant, and therefore not after a soft consonant (š ž č dž c lj nj j), after a vowel or word-initially. Because y plays an prominent role in Interslavic inflection, most declensions have a hard and a soft version because of this limitation.

In the declension of adjectives and pronouns, case endings in y become i after a soft consonant. For that reason, we have adjectives like svěž-i along with adjectives like dobr-y, and pronominal forms like moj-ih along with forms like jegov-yh.

In noun declension, however, the soft counterpart of y is always e. For example: dom-y versus kraj-e, žen-y versus zemj-e.

Because several Slavic languages do not distinguish between i and y at all, substituting all occurrences of y with i is an acceptable simplification in written Interslavic.

Ě > I

Just like y, the phoneme ě always follows a hard consonant. In the dative and locative singular of feminine nouns, it becomes i after a soft consonant, i.e. it follows a pattern opposite to y > e: žen, but zemj-i.

Fleeting o/e

A characteristic feature of the Slavic languages is the existence of "fleeting" or "movable" vowels, referring to the phenomenon of vowels appearing and disappearing in an apparently random manner, especially in certain inflected forms of nouns. This is a result of different reflexes of the Common Slavic jers ъ and ь, which were lost in a weak position and vocalised to o and e in strong position. In most cases this vowel appears in words that would otherwise end in a consonant cluster, and disappears when this cluster is followed by an ending.

Fleeting o and e appear especially in the following cases: