Sibilarization of velars before -i
In short
k → c, g → z, h → s directly before the ending -i
| Slot | k | g | h |
|---|---|---|---|
| fem. dat/loc sg | ruka → ruci | noga → nozi | svrha → svrsi |
| masc. nom pl | potok → potoci | bubreg → bubrezi | trbuh → trbusi |
| masc. dat/loc/instr pl | potocima | bubrezima | trbusima |
Feminine plural -ama keeps the consonant: rukama, nogama. -ovi plurals keep it too: vrhovi, bregovi. Names resist: Olgi, baki.
B1 · Lesson 5 · Sibilarizacija: k, g, h pred -i
The full explanation, from the lesson that teaches this rule
You already know ruka (hand, arm) and noga (leg, foot). Now look at what happens when you say "in my hand" or "on my leg": u ruci, na nozi. The k of ruka has become c, and the g of noga has become z. This is not an irregularity of two words — it is one sound rule that works across the whole language.
The rule: k, g, h meet -i
Serbian does not like the sounds k, g and h standing directly before an ending -i. When a case ending -i lands right after them, they shift to a softer hissing sound. Grammar books call this sibilarization (from sibilant, a hissing sound).
| Before -i | becomes | example |
|---|---|---|
| k | c | ruka → u ruci |
| g | z | noga → na nozi |
| h | s | trbuh → trbusi |
The rule is about the ending -i, so you only need to know where an ending -i appears. There are exactly two places.
Place 1: feminine nouns in the dative and locative singular
Feminine nouns in -a take -i in the dative and locative singular (u kući, na stolici). If the stem ends in k, g or h, the consonant changes.
| Nominative | Dative / locative singular | Example |
|---|---|---|
| ruka (hand) | ruci | Držala je cveće u ruci. |
| reka (river) | reci | Vikendica je na reci. |
| banka (where you keep money) | banci | Radim u banci. |
| noga (leg) | nozi | Imam ranu na nozi. |
| knjiga (book) | knjizi | U knjizi piše... |
| svrha (purpose) | svrsi | Pričali smo o svrsi putovanja. |
Feminine nouns in -h are rare. svrha is the one you will meet most; you will also hear svrhi, but svrsi is the standard form.
Place 2: masculine nouns in the plural
Masculine nouns take -i in the nominative plural (grad → gradovi, student → studenti). A masculine stem ending in k, g or h changes before it.
| Singular | Nominative plural | Dative / locative / instrumental plural |
|---|---|---|
| potok (stream) | potoci | potocima |
| oblak (cloud) | oblaci | oblacima |
| jezik (tongue) | jezici | jezicima |
| bubreg (kidney) | bubrezi | bubrezima |
| geolog (geologist) | geolozi | geolozima |
| trbuh (belly) | trbusi | trbusima |
| orah (walnut) | orasi | orasima |
| monah (monk) | monasi | monasima |
Notice the third column. The masculine dative, locative and instrumental plural end in -ima, and that ending is built on top of the plural stem that has already changed: potoci → potocima, bubrezi → bubrezima, trbusi → trbusima. So once you know the nominative plural, the -ima form keeps the same c, z or s.
The trap: feminine plural does NOT change
Feminine nouns in -a take -ama in the dative, locative and instrumental plural. There is no -i right after the consonant, so nothing changes: ruka → rukama, noga → nogama, reka → rekama, banka → bankama.
| Singular dative / locative | Plural dative / locative / instrumental | |
|---|---|---|
| feminine ruka | ruci (changes) | rukama (no change) |
| masculine potok | potoku (no change) | potocima (changes) |
Check the letter right after the stem. -i or -ima directly after k, g, h → change it. -a, -e, -u, -om, -ama → keep k, g, h. And the feminine nominative plural ends in -e, so it never changes: ruke, noge, reke.
When there is no -i right after the consonant
- Short masculine nouns that add -ovi in the plural put -ov- between the stem and the -i, so they keep their consonant: vrh → vrhovi (peaks), breg → bregovi (hills), rog → rogovi (horns).
- A fleeting a (the previous lesson) can disappear and bring k to the end of the stem, and then the change applies as usual: brežuljak → brežuljci → brežuljcima (little hills).
Words that resist
Personal names and a handful of family words keep their consonant, so that the name stays recognisable: Olga → Olgi, baka (grandma) → baki. Some feminine nouns in -ka also waver in everyday speech. Everything in this lesson follows the rule; treat the resisting words as exceptions you learn one by one.
Check what you read
5 of the 14 questions this lesson asks in the app. Type the form or pick the answer.
Nosim sat na levoj ___.
Moja sestra radi u(banka).
Pred vratima banke stoji čovek, a ja sam unutra, u ___.
Imam veliku modricu na desnoj(noga).
Stajao je na jednoj ___ deset minuta.
Examples from the course
The marked word is where the rule applies. Press play to hear the sentence.
Imam ranu na nozi.
I have a wound on my leg.
Bubrezi su mu zdravi.
His kidneys are healthy.
Pričali smo o svrsi putovanja.
We talked about the purpose of the trip.
Držala je cveće u ruci.
She was holding flowers in her hand.
Oblaci su sakrili vrhove planina.
The clouds hid the mountain peaks.
Radim u banci blizu reke.
I work at a bank near the river.
Šta to imaš u ruci?
What's that you have in your hand?
Polako smo se približili reci.
We slowly approached the river.
Deca leže na trbusima u travi.
The children are lying on their stomachs in the grass.
Nebo je bilo prekriveno tamnim oblacima.
The sky was covered with dark clouds.
Sentences in the course that use this rule: 142
Try it yourself
Translate a sentence that uses this rule. The check marks the word that went wrong and names the rule behind it, as in the app.
Sentences
Write it in Serbian
His kidneys are healthy.
his: the short dative form (mu), not njegovi