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Several commonly used native and assimilated loanwords have free variation between /i/ and /ɪ/ and word-initial position. In some morphemes /i/ is somewhat lowered, explained that underlying morphoneme /ɪ/ is raised under influence of a preceding soft consonant. This creates minimum acoustic contrasts between several grammar forms of adjectives of soft group, which are considered identical in phonology and orthography.
Ukrainian has no phonemic distinction between long and short vowels, however unstressed vowels are somewhat reduced in time, and as a result, in quality. Changes to /i u ɑ/ are considered not perceptible. Unstressed /ɔ/ is raised, however in many cases it is raised considerably more before syllables with high vowels /i u/, making it sound similar to /u/ ("weak o"). Such strong and weak o's are commonly differentiated in broad transcriptions, for visual distinction [ɔ] is used here for stressed and strong unstressed o, and [o] for weak unstressed o. Unstressed /ɪ/ is lowered, while unstressed /ɛ/ is raised, as a result in many unstressed positions these phonemes may be pronounced identically, with actual sound being dependant on vowel of the following syllable. Unstressed /ɛ/ is additionally raised when neighboured by soft consonant, preceding palatal consonant together with following palatalized consonant may raise it as high as near-close.
|Place of articulation →||Labial||Coronal||Dorsal||(none)|
|Manner of articulation ↓||Bilabial||Labio-
|Stop||p b||t d||tʲ dʲ||k ɡ|
|Affricate||t͡s d͡z||t͡sʲ d͡zʲ||t͡ʃ d͡ʒ|
|Fricative||f||s z||sʲ zʲ||ʃ ʒ||x||ɦ|
When consonants appear in pairs, the one to the left is voiceless and the one to the right voiced. Although /x/ and /ɦ/ do not share a place of articulation, phonologically they are a voiceless–voiced pair.
- /w/ is most commonly bilabial [β̞] before vowels  but can alternate with labio-dental [ʋ] (most commonly before /i/, also before /ɪ ɛ ɑ/). It is also vocalized to [u̯] before consonant at start of word, after vowel before consonant and after vowel at end of word.
- /t d n l s z t͡s d͡z/ are dental
- Alveolar sibilants are laminal.
- Postalveolar sibilants are somewhat rounded.
- /tʲ dʲ nʲ lʲ/ are soft counterparts to /t d n l/ and are noted for their high softness and have several possible realizations: laminal alveolo-palatal, apical alveolo-palatal, and laminal denti-palatal. The choice of symbols is based on phonological criteria rather than phonetic ones.
- All consonants except /j/ have a soft and hard variant, however this distinction is phonemic for only nine pairs. Soft variants are palatalized, and less rounded. In native words, those consonants that don't make a phonemic distinction are somewhat softer before /i/, softened labials also occur before /ɑ/ in special phonetic environments, while postalveolar geminates are softer than postalveolars before /i/. In loanwords, all of them are more common before /u ɑ/.
Gemination may occur:
- Between vowels for palatalized alveolar consonants (other than /rʲ/), and semi-palatalized allophones of postalveolar consonants.
- Between vowels across prefix-root or root-root boundaries for other coronal consonants as a result of their coincidence. In this case /w/+/w/ form [u̯β̞].
- At the start of the word for forms of the verb лити (ллю /lʲːu/, ллєш /lʲːɛʃ/, etc.), the verb ссати /sːɑtɪ/ and derivatives.
- In other cases for /n/.
When two or more consonants occur word-finally, then a vowel is epenthesized under the following conditions. Given a consonantal grouping C1(ь)C2(ь), where C is any consonant. The vowel is inserted between the two consonants and after the ь. A vowel is only inserted if C2 is either /k/, /w/, /l/, /m/, /r/, or /ts/. In this case:
- If C1 is either /w/, /ɦ/, /k/, or /x/, then the epenthisized vowel is always [o]
- No vowel is epenthesized if the /w/ is derived from a Common Slavic vocalic *l, for example, /wowk/ (see below)
- If C2 is /l/, /m/, /r/, or /ts/, then the vowel is /ɛ/.
- The combinations, /-stw/ /-sk/ are not broken up
- If the C1 is /j/ (й), then the above rules can apply. However, both forms (with and without the fill vowel) often exist
Ukrainian has a non-syllabic [ɪ̯] as an allophone of /j/. It also has a non-syllabic [u̯] as an allophone of /w/. Moreover, due to their semi-vocalic nature these sounds alternate with the vowel phonemes /i/ and /u/ respectively, the latter being used at the absolute beginning of a phrase, after a pause or after a consonant and the former following a vowel and preceding a consonant (cluster), either within a word or at a word boundary:
- він іде /win idɛ/ ('he's coming')
- вона йде /wɔnɑ jdɛ/ ('she's coming')
- він і вона /win i wɔnɑ/ ('he and she')
- вона й він /wɔnɑ j win/ ('she and he');
- Утомився вже /utɔmɪwsʲɑ wʒɛ/ ('already gotten tired')
- Уже втомився /uʒɛ wtɔmɪwsʲɑ/ ('already gotten tired')
- Він утомився. /win utɔmɪwsʲɑ/ ('he's gotten tired')
- Він у хаті. /win u xɑtʲi/ ('he's inside the house')
- Вона в хаті. /wɔnɑ w xɑtʲi/ ('she's inside the house')
- підучити /pidut͡ʃɪtɪ/ ('to learn')
- вивчити /wɪwt͡ʃɪtɪ/ ('to learn')
This feature distinguishes Ukrainian phonology remarkably from Russian and Polish, two related languages with many cognates.
Consonant assimilation 
Voiceless obstruents are voiced when preceding voiced ones, but the reverse is not true.
- [nɑʃ] ('our')
- [nɑʒ dʲid] ('our grandfather')
- [bɛrɛzɑ] ('birch')
- [bɛrɛzkɑ] ('small birch')
The exceptions are the words легко, вогко, нігті, кігті, дьогтю, дігтяр, and derivatives where /ɦ/ may be devoiced to [h], or even its phonological voiceless counterpart [x]. Prefixes ending in /z/ may be devoiced before voiceless obstruents, especially in fast speech.
Affricates are not formed across prefix-root, or root-root boundaries, or across word boundaries, however they are formed across left boundaries of suffixes /sʲk/ and /stw/.
Sibilant consonants (including affricates) in clusters assimilate place of articulation and palatalization state of the last segment in a cluster. The most common case of such assimilation is verbal ending -шся where |ʃsʲɑ| assimilates into /sʲːɑ/. This assimilation is specific to morpheme boundaries because such clusters don't occur within one morpheme.
Historical phonological changes 
In the Ukrainian language, the following sound changes have occurred between the Common Slavic period and current Ukrainian:
- In a newly closed syllable, that is, a syllable that ends in a consonant, Common Slavic *o and *e mutated into *i if the next vowel was one of the yers (*ĭ/ь or *ŭ/ъ).
- Pleophony: The Common Slavic combinations, CoLC and CeLC, where L is either *r or *l become in Ukrainian
- CorC gives CoroC (Common Slavic *borda gives Ukrainian boroda)
- ColC gives ColoC (Common Slavic *bolto gives Ukrainian boloto)
- CerC gives CereC (Common Slavic *berza gives Ukrainian bereza)
- CelC gives ColoC (Common Slavic *melko gives Ukrainian moloko)
- The Common Slavic nasal vowel *ę is reflected as /jɑ/; a preceding labial consonant generally was not palatalized after this, and after a postalveolar it became /ɑ/ Examples: Common Slavic *pętĭ became Ukrainian /pjɑt/ (п’ять); Common Slavic *telę became Ukrainian /tɛlʲɑ/; and Common Slavic *kurčę became Ukrainian /kurt͡ʃɑ/.
- Common Slavic *ě (Cyrillic ѣ), generally became Ukrainian /i/ except:
- word-initially, where it became /ji/: Common Slavic *ěsti became Ukrainian /jistɪ/
- after the post-alveolar sibilants where it became /ɑ/: Common Slavic *ležěti became Ukrainian /lɛʒɑtɪ/
- Common Slavic *i and *y are both reflected in Ukrainian as /ɪ/
- The Common Slavic combination -CǐjV, where V is any vowel, became -CʲCʲV, except:
- if C is labial or /r/ where it became -CjV
- if V is the Common Slavic *e, then the vowel in Ukrainian mutated to /ɑ/, e.g., Common Slavic *žitĭje became Ukrainian /ʒɪtʲːɑ/
- if V is Common Slavic *ĭ, then the combination became /ɛj/, e.g., genitive plural in Common Slavic *myšĭjĭ became Ukrainian /mɪʃɛj/
- if one or more consonants precede C then there is no doubling of the consonants in Ukrainian
- Sometime around the early thirteenth century, the voiced velar stop lenited to [ɣ] (except in the cluster *zg). Within a century, /ɡ/ was reintroduced from Western European loanwords and, around the sixteenth century, [ɣ] debuccalized to [ɦ].
- Common Slavic combinations *dl and *tl were simplified to /l/, for example, Common Slavic *mydlo became Ukrainian /mɪlɔ/
- Common Slavic *ǔl (vocalic *l̥) and *ǐl (vocalic ĺ̥) became /ɔw/. For example, Common Slavic *vĺ̥kǔ became /wɔwk/ in Ukrainian.
- Русанівський, Тараненко & Зяблюк (2004:104)
- Жовтобрюх & Кулик (1965:117–118)
- Русанівський, Тараненко & Зяблюк (2004:407)
- Жовтобрюх & Кулик (1965:121–122)
- Русанівський, Тараненко & Зяблюк (2004:522–523)
- S. Buk, J. Mačutek, A. Rovenchak (2008). "Some properties of the Ukrainian writing system". Retrieved April 19, 2013.
- Русанівський, Тараненко & Зяблюк (2004:581)
- Carlton, T.R. A Guide to the Declension of Nouns in Ukrainian. Edmonton, Alberta: University of Alberta Press, 1972
- Mascaró & Wetzels (2001:209)
- Shevelov (1977:145)
- Shevelov (1977:148)
- Mascaró, Joan; Wetzels, W. Leo (2001). "The Typology of Voicing and Devoicing". Language 77 (2): 207–244. doi:10.1353/lan.2001.0123.
- Shevelov, George Y. (1977). "On the Chronology of h and the New g in Ukrainian". Harvard Ukrainian Studies (Cambridge: Harvard Ukrainian Research Institute) 1 (2): 137–52.
- Русанівський, В. М.; Тараненко, О. О.; Зяблюк, М. П. та ін. (2004). Українська мова: Енциклопедія. ISBN 978-966-7492-19-9.
- Жовтобрюх, М.А.; Кулик, Б.М. (1965). Курс сучасної української літературної мови. Частина I. Kiev: Радянська школа.
Further reading 
- Ukrainian IPA by Tonia Bilous, Весна, December 5, 2005, retrieved December 5, 2005 (Ukrainian language: UkrIPA.pdf, UkrIPA.doc)
- Zilyns'kyj, I. (1979). A Phonetic Description of the Ukrainian Language. Harvard University Press. ISBN 0-674-66612-7..
- Багмут, Алла Йосипівна (1980). Інтонація як засіб мовної комунікації. Kiev: Наукова думка.
- Тоцька, Н.І. (1973). Голосні фонеми української літературної мови. Kiev: Київський університет.
- Тоцька, Н.І. (1995). Сучасна українська літературна мова. Kiev: Вища школа.