Voicing Assimilation in Clusters

When two obstruents (the "noisy" consonants — stops, fricatives, affricates) bump into each other inside a Croatian word, they must agree on one thing: whether the vocal cords are vibrating. This is voicing assimilation, in Croatian jednačenje suglasnika po zvučnosti ("matching of consonants by voicing"). The rule is simple to state — the second consonant decides, and the first one falls into line — but the genuinely Croatian twist, the thing that sets it apart from Russian or Polish, is that Croatian writes most of these changes into the spelling. So this is not only a pronunciation rule; it is also a spelling rule, and getting it wrong produces a real spelling error, not just an accent.

The voiced / voiceless pairs

Every obstruent in Croatian has a "twin" that is articulated in the same place and manner but differs only in voicing. Assimilation simply swaps a consonant for its twin.

Three voiceless consonants — f, h, c — have no voiced partner, so they can trigger devoicing in a neighbour but never become voiced themselves. The sonorants (j, l, lj, m, n, nj, r, v) sit outside the system entirely: they neither cause assimilation nor undergo it. (The behaviour of v at boundaries is a special case we will come back to.)

The rule is regressive: look rightward

Assimilation in Croatian is regressive (also called anticipatory): the consonant on the right dictates, and the consonant on the left changes to match it. Your mouth, in effect, gets the second sound ready early and pulls the first one into the same voicing setting. This is why you must always look at what follows.

Voiced → voiceless (devoicing before a voiceless consonant)

This is by far the most common direction, because it surfaces whenever a voiced-final stem meets a voiceless suffix. The classic trigger is the masculine-adjective ending -ka / -ko on a stem ending in a voiced stop.

The masculine form is gladak (smooth), with a d. Add the feminine ending -ka and the d stands directly before the voiceless k: it devoices to t, and — crucially — the spelling changes too: glatka, glatko, not gladka.

Same machinery: sladak (sweet) → slatka, slatko, slatki. The d before k is written t.

The adjective težak (heavy) keeps its ž here because it stands before a vowel. But watch what happens in the feminine and in the comparative-related forms where ž meets a voiceless consonant.

Težak → teška: the ž stands before voiceless k and devoices to š, written š. Again the spelling records the change.

Voiceless → voiced (voicing before a voiced consonant)

The reverse also happens, though it is rarer: a voiceless consonant becomes voiced before a voiced obstruent. The textbook case is the noun svadba (wedding), built from the root of svat (wedding guest).

The root has a t (svatovi "wedding guests"), but in svadba the t stands before voiced b and voices to d — and that is how it is spelled: svadba, never svatba.

Ropstvo (bondage) is built from rob (slave) plus -stvo. Here the voiced b of rob meets the voiceless s of -stvo and devoices to p: rob + stvo → ropstvo. The spelling shows the p.

Watch the alternation in vrabac (sparrow). The nominative singular has b, but in oblique forms the fleeting a drops out and the b ends up before voiceless c: vrabac → vrapca, vrapci. The b devoices to p in writing — vrapca, not vrabca. The dropping vowel that creates this collision is the fleeting a.

Why Croatian writes it down and Russian does not

This is the single most useful thing to understand on this page. Both Russian and Croatian pronounce these assimilations — the Russian word for "sweet," like Croatian slatka, has a voiceless [t] before the [k]. The difference is orthographic philosophy. Russian spelling (in its Cyrillic script) is morphophonemic: it keeps the underlying root letter constant — it writes the "d" of the root even though you say [t] — so the reader recovers the morpheme. Croatian spelling is phonological: by Ljudevit Gaj's principle "write as you speak," it writes the sound that actually comes out. So Croatian writes slatka, teška, vrapca, ropstvo — the assimilation is baked into the orthography.

The exceptions you must know

Croatian's "write what you say" principle has a handful of deliberate exceptions, kept to preserve morphological transparency. These are tested in school spelling and are exactly where learners (and natives) slip.

1. No devoicing of d before s or š

The cluster ds / dš is left alone in writing, even though casual speech may blur it. This protects recognisable prefixes like pod-, od-, nad-, pred-.

Predsjednik (president) keeps its d before s: pred- + sjednik. You do not write pretsjednik, even though you may hear something close to it.

Odšteta (compensation) keeps d before š by the same exception.

2. The change is not written before v (and other sonorants)

Because sonorants do not take part in voicing, a voiceless consonant before v is not voiced in spelling — this is why we get tvoj, svoj, cvijet, kvar with their voiceless first consonant intact, and why -stvo survives in bogatstvo (wealth) and društvo (society).

3. Across some word-internal boundaries the prefix is protected

A few prefixed forms keep the prefix consonant for clarity even where assimilation might be expected.

Gradski (urban, "city-") keeps its d before s — same family of exceptions as predsjednik. The root grad (city) stays visible.

Word-final position: Croatian is NOT German or Russian

Here is another point where Croatian quietly diverges from its Slavic and Germanic neighbours. German devoices every final obstruent in pronunciation (Tag sounds like [tak]), and Russian does the same — its word for "city," though written with a final voiced letter in Cyrillic, is pronounced ending in [t]. Standard Croatian does not write final devoicing, and the careful spoken norm largely keeps the voiced consonant.

Grad (town) is written with a final d and, in standard careful speech, pronounced with a voiced [d]. You will hear some phonetic devoicing in casual speech — a final consonant is naturally weaker — but it is not a categorical rule, and it is never reflected in spelling.

Bog (god) keeps its written g; you are not expected to say or write bok (which, incidentally, is a separate word — the Zagreb greeting "hi").

Nož (knife) is written and standardly pronounced with a voiced final ž.

Common mistakes

Key takeaways

• Voicing assimilation is regressive: the second obstruent in a cluster decides the voicing of the first.
• Croatian, unlike Russian, writes the change into the spelling (slatka, teška, vrapca, svadba, ropstvo), so it is a spelling rule as much as a pronunciation rule.
• Key exceptions kept in writing: d stays before s/š (predsjednik, gradski, odšteta), and nothing changes before v or other sonorants (-stvo).
• Croatian does not write word-final devoicing — grad, bog, nož keep their voiced letters, unlike German or Russian.
• Your effort goes into writing: when you inflect or build a word, apply the change yourself. See also sound-change spelling and clusters and devoicing.