Sound laws
Regular correspondences from Proto-Slavic into the five languages. Learn a law once and it decodes hundreds of words.
1 · r and l
Pleophony and liquid metathesis
*CorC, *ColC, *CerC, *CelC
Proto-Slavic allowed syllables like *gor-dъ, with o or e followed by r or l before another consonant. Late in the Common Slavic period (roughly 8th–9th c.) every dialect repaired them: East Slavic added a copy of the vowel after the liquid (pleophony, полногласие), while West and South Slavic swapped the vowel and the liquid (liquid metathesis) — Czech and BCS with a long vowel, Polish with a short one.
Outcomes
- Russian
- -оро- -оло- -ере- (pleophony)
- Ukrainian
- -оро- -оло- -ере- (pleophony)
- Polish
- -ro- -ło- -rze- -le-
- Czech
- -ra- -la- -ře- -le- (often long: -rá-)
- Bosnian-Croatian-Serbian
- -ra- -la- -re- -le-
Examples
*gordъ enclosure, town
RU го́родUK горо́дPL gródCS hradBCS grad
*golva head
RU голова́UK голова́PL głowaCS hlavaBCS glava
*korva cow
RU коро́ваUK коро́ваPL krowaCS krávaBCS krava
*vorna crow
RU воро́наUK воро́наPL wronaCS vránaBCS vrana
*bergъ shore, bank
RU бе́регUK бе́регPL brzegCS břehBCS brijeg
*melko milk
RU молоко́UK молоко́PL mlekoCS mlékoBCS mlijeko
Exceptions: Russian took many Church Slavonic forms with the South Slavic shape, so it has doublets: голова́ 'head' / глава́ 'chapter', сторона́ 'side' / страна́ 'country', го́род / -град in names (Волгогра́д). Ukrainian горо́д today means 'vegetable garden'. In *melko the e became o after l in East Slavic.
Words in Slovo that show it: king, enemy, head, hair (on the head), beard, health, palm (of the hand), cloud, frost, shore, bank, gold, swamp, marsh, cow, crow, tree, birch, milk, hammer, town, city, road, gate, country, time, Wednesday, young, short, cold, empty, sweet, dear, expensive, hungry, to die, shame, voice, hi, hello
2 · r and l
*or-, *ol- at the start of a word
#orC-, #olC-
The same urge to open syllables met words that began with *or- or *ol-. Here the liquid and vowel swapped everywhere, but the vowel's quality depended on the old accent and the region: South Slavic always has ra-/la-; North Slavic has ro-/lo- unless the syllable carried the rising (acute) tone, in which case it too has ra-/la-.
Outcomes
- Russian
- ро- ло- (ра- ла- under the old rising tone)
- Ukrainian
- ро- ло- (ра- ла- under the old rising tone)
- Polish
- ro- ło- (ra- ła- under the old rising tone)
- Czech
- ro- lo- (ra- la- under the old rising tone)
- Bosnian-Croatian-Serbian
- ra- la- (always)
Examples
*orvьnъ level, even
RU ро́вныйUK рі́внийPL równyCS rovnýBCS ravan
*olkъtь elbow
RU ло́котьUK лі́котьPL łokiećCS loketBCS lakat
*ordlo simple plough
RU ра́лоUK ра́лоPL radłoCS rádloBCS ralo
*orbota servitude, work
RU рабо́таUK робо́таPL robotaCS robotaBCS rabota
Exceptions: Russian рабо́та has the South Slavic ra-, usually explained as Church Slavonic influence; the native shape survives in Ukrainian робо́та and Russian dialects. BCS rabota is colloquial; the everyday word for work is rad or posao.
Words in Slovo that show it: elbow, work, job, boat, mind, intellect, to understand
3 · r and l
Syllabic r and l
*CьrC, *CъrC, *CьlC, *CъlC
Sequences of a yer plus r or l between consonants (*vьlkъ, *tъrgъ) turned into syllabic liquids in Czech and BCS, which is why Czech can say 'Strč prst skrz krk' and BCS 'vrh', 'trg' with no vowel letters. East Slavic and Polish turned the yer into a full vowel instead. BCS later vocalized syllabic l to u (vuk, pun), and Ukrainian turned the l into в [w].
Outcomes
- Russian
- -ер- -ор- -ол- (-ёл-)
- Ukrainian
- -ер- -ор- -ов- (l → в)
- Polish
- -ar- -ier- -ił- -eł- -ół-
- Czech
- syllabic r l (vlk, trh)
- Bosnian-Croatian-Serbian
- syllabic r; syllabic l → u
Examples
*vьlkъ wolf
RU волкUK вовкPL wilkCS vlkBCS vuk
*vьrxъ top
RU верхUK верхPL wierzchCS vrchBCS vrh
*tъrgъ market
RU торгUK торгPL targCS trhBCS trg
*žьltъ yellow
RU жёлтыйUK жо́втийPL żółtyCS žlutýBCS žut
*pьlnъ full
RU по́лныйUK по́внийPL pełnyCS plnýBCS pun
*sьrdьce heart
RU се́рдцеUK се́рцеPL serceCS srdceBCS srce
Exceptions: Czech syllabic l sometimes became lu (žlutý, dlouhý 'long' from *dьlgъ).
Words in Slovo that show it: finger, heart, throat, tear (from crying), sun, hill, wolf, worm, pot, saucepan, mirror, market, church, Thursday, long, full, black, red, yellow, hard, firm, to hold
4 · Vowels
Jat (ě) and its reflexes
*ě
Proto-Slavic jat (*ě), written ѣ in old Cyrillic, was a long front vowel whose exact value differed by region. Each language resolved it its own way, and BCS split three ways — the basis of the ijekavian/ekavian difference between the standards (mlijeko vs mleko). Russian merged it with е; the letter ѣ was dropped from Russian spelling only in 1918.
Outcomes
- Russian
- е
- Ukrainian
- і
- Polish
- ia before a hard dental, ie elsewhere
- Czech
- ě / e (í when long)
- Bosnian-Croatian-Serbian
- ije / je (ijekavian), e (ekavian), i (ikavian dialects)
Examples
*světъ world, light
RU светUK світPL światCS světBCS svijet
*měsęcь moon, month
RU ме́сяцUK мі́сяцьPL miesiącCS měsícBCS mjesec
*rěka river
RU река́UK ріка́PL rzekaCS řekaBCS rijeka
*věra faith
RU ве́раUK ві́раPL wiaraCS víraBCS vjera
*sněgъ snow
RU снегUK снігPL śniegCS sníhBCS snijeg
*bělъ white
RU бе́лыйUK бі́лийPL białyCS bílýBCS bijel
Exceptions: BCS examples are ijekavian; ekavian has svet, mesec, reka, vera, sneg, beo. After r, short jat gives e even in ijekavian (repa, brijeg vs bregovi). Russian has ё from jat in a few words (звёзды, гнёзда).
Words in Slovo that show it: grandfather, person, human being, child, neighbour, family, girl, young woman, bride, fiancée, knee, body, moon, star, snow, wind, river, forest, woods, sand, light, world, shadow, shade, iron, bear, flower, nut, walnut, bread, dough, lunch, main midday meal, wall, candle, bucket, price, doctor, time, month, summer, Monday, Wednesday, Sunday, white, bright, light-coloured, poor, fresh, to do, to make, to go (by vehicle), to ride, to see, to die, to sit, to be sitting, to sing, to want, to run, to fly, anger, hope, faith, belief, song, to understand, to believe
5 · Vowels
Nasal vowels (ę, ǫ)
*ę, *ǫ
Proto-Slavic had two nasal vowels. Polish is the only one of the five that kept them (written ę and ą), though it reshuffled them by length: short nasals became ę, long ones ą — so *rǫka gave ręka and *zǫbъ gave ząb. Everywhere else they lost their nasality by about the 10th–11th century.
Outcomes
- Russian
- я (ę), у (ǫ)
- Ukrainian
- я (ę), у (ǫ)
- Polish
- ę / ą — still nasal
- Czech
- e, ě, á (ę); u, ou (ǫ)
- Bosnian-Croatian-Serbian
- e (ę), u (ǫ)
Examples
*rǫka hand
RU рука́UK рука́PL rękaCS rukaBCS ruka
*zǫbъ tooth
RU зубUK зубPL ząbCS zubBCS zub
*dǫbъ oak
RU дубUK дубPL dąbCS dubBCS dub
*pętь five
RU пятьUK п’ятьPL pięćCS pětBCS pet
*językъ tongue, language
RU язы́кUK язи́кPL językCS jazykBCS jezik
*męso meat
RU мя́соUK м’я́соPL mięsoCS masoBCS meso
Exceptions: Polish ę and ą alternate inside one word family (ręka – rąk, ząb – zęby) because length alternated. Spoken Polish pronounces them as vowel + nasal consonant before stops (ząb [zɔmp]) and denasalizes final ę.
Words in Slovo that show it: husband, man (male), neighbour, prince, name, tooth, tongue, hand, arm, shoulder, meadow, hare, goose, duck, oak, meat, flour, book, towel, glove, money, court (of law), five, nine, ten, thousand, month, Friday, narrow, heavy, hot, wise, clever, to begin, to start, language, memory, happiness, luck, to remember
6 · Yers
The fall of the yers
*ъ, *ь
Proto-Slavic had two ultra-short vowels, the yers ъ and ь. Around the 10th–12th centuries they were lost or strengthened by Havlík's law: counting back from the end of the word, a yer at the end or before a syllable with a full vowel was weak and disappeared; one before a weak yer was strong and became a full vowel — a different vowel in each language. This is why vowels appear and vanish inside one word: сон – сна, pies – psa, pes – psa, pas – psa.
Outcomes
- Russian
- strong ъ → о, ь → е; weak lost
- Ukrainian
- strong ъ → о, ь → е; weak lost
- Polish
- strong → e (ie); weak lost
- Czech
- strong → e; weak lost
- Bosnian-Croatian-Serbian
- strong → a; weak lost
Examples
*sъnъ sleep, dream
RU сонUK сонPL senCS senBCS san
*dьnь day
RU деньUK деньPL dzieńCS denBCS dan
*pьsъ dog
RU пёсUK песPL piesCS pesBCS pas
*otьcь father
RU оте́цUK оте́цьPL ojciecCS otecBCS otac
*mъxъ moss
RU мохUK мохPL mechCS mechBCS mah
Exceptions: Analogy often restores a vowel across a paradigm (Russian лёд – льда but день – дня), and the hard sign ъ survives in Russian spelling only as a separator (подъе́зд). BCS a from yers is the quickest way to spot a BCS word: san, dan, pas, otac.
Words in Slovo that show it: father, prince, widow, heart, blood, elbow, eyebrow, health, nail (finger, toe), sun, rain, wind, hill, sand, fire, ice, dog, horse, ox, sheep, wolf, bird, bee, apple, salt, honey, garlic, pepper (spice), house, door, bed, knife, spoon, drinking glass, pot, saucepan, book, needle, thread, village, castle, one, seven, eight, day, today, yesterday, Tuesday, bad, short, low, narrow, heavy, light (not heavy), sweet, bitter, dark, strong, poor, to take, to sleep, to write, to play, to open, truth, lie, falsehood, love, joy, dream; sleep, thought, honour, happiness, luck, he, who, what, this, everything, all, where, much, a lot, always, with, in
7 · Vowels
e → o before a hard consonant (ё)
*e (and strong *ь) before a hard consonant
From about the 12th century, East Slavic e before a hard (non-palatal) consonant became o — in Russian only under stress, where it is written ё; in Ukrainian mainly after the hushing consonants ж ч ш. Polish had its own, older version of the same shift (see Polish vowel ablaut). Czech and BCS keep e.
Outcomes
- Russian
- ё [jo, o] under stress
- Ukrainian
- о after ж ч ш (and й)
- Polish
- o / io (see Polish ablaut)
- Czech
- e (no change)
- Bosnian-Croatian-Serbian
- e (no change)
Examples
*medъ honey
RU мёдUK медPL miódCS medBCS med
*ledъ ice
RU лёдUK лідPL lódCS ledBCS led
*čьrnъ black
RU чёрныйUK чо́рнийPL czarnyCS černýBCS crn
*žьltъ yellow
RU жёлтыйUK жо́втийPL żółtyCS žlutýBCS žut
*šestъ sixth
RU шесто́йUK шо́стийPL szóstyCS šestýBCS šesti
Exceptions: Church Slavonic words never have ё: Russian небо 'sky' (but нёбо 'palate', the native twin), крест. Russian writing often omits the dots, so ё is spelled е in most printed texts.
Words in Slovo that show it: ice, dog, bee, birch, honey, garlic, broom, yesterday, light (not heavy), warm, black, green, yellow, dark, hard, firm
8 · Vowels
Polish vowel ablaut (ě → a, e → o)
*ě, *e, *ę before a hard dental
In Polish and the other Lechitic languages, front vowels became back vowels before a hard dental consonant (t, d, s, z, n, r, ł): ě → a, e → o, softening the consonant before them. Because the next consonant decides, Polish words alternate inside one paradigm: wiara 'faith' but wierzyć 'believe', lato 'summer' but w lecie 'in summer', siostra but siostrze.
Outcomes
- Russian
- е (no shift)
- Ukrainian
- і / е (no shift)
- Polish
- ia ← ě, io ← e, ą ← ę before t d s z n r ł
- Czech
- ě / e (no shift)
- Bosnian-Croatian-Serbian
- ije / je / e (no shift)
Examples
*lěto summer
RU ле́тоUK лі́тоPL latoCS létoBCS ljeto
*sestra sister
RU сестра́UK сестра́PL siostraCS sestraBCS sestra
*jezero lake
RU о́зероUK о́зероPL jezioroCS jezeroBCS jezero
*gnězdo nest
RU гнездо́UK гніздо́PL gniazdoCS hnízdoBCS gnijezdo
*bělъ white
RU бе́лыйUK бі́лийPL białyCS bílýBCS bijel
Exceptions: Russian and Ukrainian о́зеро start with o- for an unrelated reason (East Slavic *je- → o- at the start of a word, as in оди́н vs jeden).
Words in Slovo that show it: sister, grandfather, wife, neighbour, knee, body, star, wind, lake, forest, woods, sand, light, world, iron, feather, flower, honey, dough, lunch, main midday meal, wall, bucket, broom, evening, spring (season), summer, Monday, Wednesday, white, green, faith, belief
9 · Consonants
g → h (spirantization)
*g
Between roughly the 12th and 14th centuries, a belt of Slavic languages — Ukrainian, Belarusian, Czech, Slovak and Upper Sorbian — turned *g into a voiced fricative h [ɦ]. Russian, Polish and BCS kept the stop. Ukrainian spells the new sound with the same letter г, so Russian and Ukrainian голова́ look identical but sound different.
Outcomes
- Russian
- г [ɡ]
- Ukrainian
- г [ɦ]
- Polish
- g
- Czech
- h [ɦ]
- Bosnian-Croatian-Serbian
- g
Examples
*gora mountain
RU гора́UK гора́PL góraCS horaBCS gora
*golva head
RU голова́UK голова́PL głowaCS hlavaBCS glava
*noga leg, foot
RU нога́UK нога́PL nogaCS nohaBCS noga
*gostь guest
RU гостьUK гістьPL gośćCS hostBCS gost
*bogъ god
RU богUK богPL bógCS bůhBCS bog
Exceptions: Both languages got a new [ɡ] later from loans: Ukrainian writes it ґ (ґа́нок 'porch', ґу́дзик 'button'), Czech writes g (guma, gól). Russian г is pronounced [v] in the genitive ending -ого and [x] in a few words (бог [box]).
Words in Slovo that show it: guest, head, leg, foot, throat, chest, breast, nail (finger, toe), star, snow, mountain, fire, shore, bank, thunder, goose, mushroom, berry, pot, saucepan, book, needle, market, border, hour, long, hot, bitter, rich, dear, expensive, stupid, hungry, to speak, to talk, to play, to cook, to prepare, to lose, can, to be able, to help, anger, voice
10 · Vowels
Ukrainian і (ikavism)
*ě; *o, *e in a newly closed syllable
Ukrainian has і in two sets of words: where Proto-Slavic had jat (хліб, світ), and where o or e stood in a syllable that became closed when a following weak yer was lost (*konь → кінь, *noktь → ніч). The second set alternates in the paradigm: кінь – коня́, ніч – но́чі, піч – пе́чі. Czech and Polish lengthened the same vowels instead, which is why Czech ů and Polish ó often line up with Ukrainian і.
Outcomes
- Russian
- е (ě); о, е
- Ukrainian
- і
- Polish
- ia/ie (ě); o → ó, e
- Czech
- ě/í (ě); o → ů, e
- Bosnian-Croatian-Serbian
- ije/je/e (ě); o, e
Examples
*konь horse
RU коньUK кіньPL końCS kůňBCS konj
*domъ house
RU домUK дімPL domCS důmBCS dom
*noktь night
RU ночьUK нічPL nocCS nocBCS noć
*xlěbъ bread
RU хлебUK хлібPL chlebCS chlébBCS hljeb
*ledъ ice
RU лёдUK лідPL lódCS ledBCS led
*sedmь seven
RU семьUK сімPL siedemCS sedmBCS sedam
Exceptions: Ukrainian і from o/e appears only in closed syllables, so forms with an ending keep o/e: кінь – коня́, дім – до́му. Croatian uses kruh for bread; hljeb/hleb is the reflex used in the other standards.
Words in Slovo that show it: grandfather, woman, guest, neighbour, family, kin, lineage, nose, bone, belly, stomach, knee, elbow, body, nail (finger, toe), moon, snow, wind, river, forest, woods, stone, light, world, shadow, shade, island, ice, thunder, iron, cat, horse, ox, sheep, bear, flower, nut, walnut, root, bread, salt, dough, lunch, main midday meal, house, window, wall, table, bed, stove, oven, knife, candle, bucket, broom, courtyard, yard, bridge, price, doctor, war, six, seven, eight, night, evening, month, summer, autumn, fall, Monday, Sunday, bitter, white, bright, light-coloured, poor, fresh, to go (by vehicle), to ride, to eat, to sit, to be sitting, to sing, to open, to want, to run, to fly, joy, anger, hope, faith, belief, song, to understand, to believe, he
11 · Consonants
*tj and *dj
*tj, *dj (and *kt, *gt before a front vowel)
The clusters *tj and *dj (and *kt/*gt before a front vowel) palatalized differently in each branch, and the result is one of the clearest signatures of a Slavic language: East Slavic ч/ж, West Slavic c/dz (z in Czech), BCS ć/đ — and the Church Slavonic щ/жд that Russian borrowed alongside its native forms.
Outcomes
- Russian
- ч, ж (Church Slavonic щ, жд)
- Ukrainian
- ч, ж (дж in verbs)
- Polish
- c, dz
- Czech
- c, z
- Bosnian-Croatian-Serbian
- ć, đ
Examples
*světja candle
RU свеча́UK сві́чкаPL świecaCS svíceBCS svijeća
*medja boundary
RU межа́UK межа́PL miedzaCS mezBCS međa
*noktь night
RU ночьUK нічPL nocCS nocBCS noć
*pektь oven, stove
RU печьUK пічPL piecCS pecBCS peć
Exceptions: Russian doublets: native свеча́ vs Church Slavonic освеще́ние 'lighting'; native надёжа (dialect) vs Church Slavonic наде́жда 'hope'; мощь 'might' (Church Slavonic) beside Polish moc, Czech moc, BCS moć.
Words in Slovo that show it: daughter, food, fruit, vegetable, stove, oven, footwear, shoes, candle, thousand, night, hot, hope, help, goodbye
12 · Consonants
Soft r → Polish rz, Czech ř
*r before a front vowel or *j
A palatalized r became a fricative in Polish, written rz (and now pronounced like ż), and in Czech the famous ř, a trilled fricative found in almost no other language. Russian keeps a soft r; BCS and Ukrainian lost most r palatalization.
Outcomes
- Russian
- р [rʲ]
- Ukrainian
- р (soft before і, hard before е)
- Polish
- rz [ʐ]
- Czech
- ř [r̝]
- Bosnian-Croatian-Serbian
- r
Examples
*rěka river
RU река́UK ріка́PL rzekaCS řekaBCS rijeka
*morje sea
RU мо́реUK мо́реPL morzeCS mořeBCS more
*trьje three
RU триUK триPL trzyCS třiBCS tri
*bergъ shore
RU бе́регUK бе́регPL brzegCS břehBCS brijeg
*rěpa turnip
RU ре́паUK рі́паPL rzepaCS řepaBCS repa
Exceptions: Polish rz and ż sound the same today ([ʐ]); spelling keeps the history: rz from r, ż from *ž.
Words in Slovo that show it: friend, river, sea, shore, bank, tree, birch, mushroom, nut, walnut, root, pepper (spice), dinner, supper, door, roof, doctor, three, four, bitter, to come, to arrive, to die, to believe
13 · Vowels
Czech vowel shifts (přehláska, ú → ou)
*a, *u after a soft consonant; long *ū, *ō
Old Czech fronted a and u after soft consonants (přehláska, 13th–14th c.): *duša → duše, *ključь → klíč, *ljudьje → lidé. Later long ú became the diphthong ou (*mǫka → mouka) and long ó became ů (kůň, dům). These shifts make Czech look most different from its neighbours.
Outcomes
- Russian
- а, у (no change)
- Ukrainian
- а, у (no change)
- Polish
- a, u (no change)
- Czech
- a → e/ě, u → i after soft; ú → ou; ó → ů
- Bosnian-Croatian-Serbian
- a, u (no change)
Examples
*duša soul
RU душа́UK душа́PL duszaCS dušeBCS duša
*ključь key
RU ключUK ключPL kluczCS klíčBCS ključ
*ljudьje people
RU лю́диUK лю́диPL ludzieCS lidéBCS ljudi
*mǫka flour; torment
RU мука́UK мука́PL mąkaCS moukaBCS muka
*čaša cup
RU ча́шаUK ча́шаPL czaszaCS číšeBCS čaša
*jajьce egg
RU яйцо́UK яйце́PL jajoCS vejceBCS jaje
Exceptions: Spoken Czech goes further (ý → ej, é → í: dobrej, mlíko); the standard keeps ý and é. BCS muka today means 'torment' (and 'flour' only regionally; the usual word is brašno).
Words in Slovo that show it: neighbour, people (persons), meadow, fly (insect), egg, porridge, kasha, flour, dinner, supper, key, street, border, court (of law), Sunday, long, wise, clever, stupid, to buy, to wait
14 · r and l
BCS syllable-final l → o
*l at the end of a syllable
In the 14th century Shtokavian — the dialect behind all the BCS standards — vocalized l at the end of a syllable to o (and syllabic l to u). So the forms with an ending keep the l (kotao – kotla, orao – orla) while the base form has o. Polish ł, now pronounced [w], is a softer echo of the same tendency.
Outcomes
- Russian
- л
- Ukrainian
- л (в after o in some words: вовк)
- Polish
- ł [w]
- Czech
- l
- Bosnian-Croatian-Serbian
- o
Examples
*pepelъ ash
RU пе́пелUK по́пілPL popiółCS popelBCS pepeo
*kotьlъ kettle, cauldron
RU котёлUK коте́лPL kociołCS kotelBCS kotao
*orьlъ eagle
RU орёлUK оре́лPL orzełCS orelBCS orao
*sokolъ falcon
RU со́колUK со́кілPL sokółCS sokolBCS soko
*vьlkъ wolf
RU волкUK вовкPL wilkCS vlkBCS vuk
Exceptions: The standards differ on 'table': Croatian stol keeps the l, the other standards have sto. Past participles show the rule in every verb: bio, išao, rekao (from bil-, išl-, rekl-).
Words in Slovo that show it: ox, salt, table, warm, white, bright, light-coloured, thought