The Serbian Instrumental Case
The instrumental case is the part of Serbian that finally makes English speakers slow down, because it does two jobs that English handles with little words, and Serbian handles with an ending. The first job is means: the tool, the instrument, or the transport you use to do something. It answers the question "by what?" (in Serbian, "čime?"). Here is the part that trips up almost every English speaker: there is no preposition at all. You just change the end of the noun. "Putujem vozom." means "I travel by train." "Pišem olovkom." means "I write with a pen." "Sečem hleb nožem." means "I cut bread with a knife." In English you reach for "by" or "with" every single time, and that habit is exactly what you have to unlearn. Serbian packs "by" and "with" straight into the word, so the preposition simply disappears. The second job is company: the person you are with. It answers "with whom?" ("s kim?"), and this time you do need a preposition, the little word s or sa. "Idem sa sestrom." means "I'm going with my sister." So the split is the whole game: means takes no preposition, company takes s/sa. That split is where the classic mistake lives. Learners feel that "with a knife" and "with my sister" are the same "with," so they add s/sa to everything. They say "Idem s vozom" or "Idem sa autobusom," which lands on a Serbian ear as if the bus were a travelling companion. The correct forms are "Idem vozom" and "Idem autobusom." Use s/sa only for people. Even native speakers occasionally slip here, so you are in good company, but the rule is firm. You can also stack both jobs in one sentence: "Putujem autobusom sa prijateljem." — "I'm travelling by bus with a friend." Bus is the means (no preposition), the friend is the company (sa). Now the endings, which are mercifully tidy in the singular. Hard-stem nouns take -om: voz becomes vozom, auto becomes autom, pero becomes perom, kafa becomes kafom, olovka becomes olovkom. Soft-stem nouns, the ones ending in j, č, ž, š or c, take -em instead: nož becomes nožem, muž becomes mužem. In the plural, the ending is -ima across the board. One last detail on the preposition itself: choose sa (not s) before words starting with s, z, š or ž, and always say "sa mnom" for "with me." So it's "sa sestrom" and "sa Žarkom," but "s bratom" and "s mamom." It is purely about what sounds clean out loud. Get the no-preposition habit for transport, keep s/sa for people, and the instrumental stops feeling foreign fast.
Examples
- Putujem vozom. I travel by train.
- Pišem olovkom. I write with a pen.
- Idem sa sestrom. I'm going with my sister.
The full lesson
Everything in the video, in text.
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You travel by train, you write with a pen, you go with your sister. By what? With whom? In Serbian one case covers all of that — the instrumental. Master it and you instantly sound more natural. Let's nail it down completely.
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The instrumental has two main jobs. First, it marks the MEANS — the tool or way you do something, the by means of what. Second, it marks COMPANY — the person you're with. It answers by what? (čime?) and with whom? (s kim?).
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Here are the endings. Masculine and neuter take -om: voz becomes vozom, auto becomes autom. Feminine in -a also takes -om: kafa becomes kafom, olovka becomes olovkom. One ending for almost everything — that's the heart of the instrumental.
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Let's start with transport, because that's the biggest trap. How do you travel? Vozom — and with no preposition at all. Putujem vozom. I travel by train. Voz takes -om and becomes vozom. The ending alone carries the meaning by train, by means of the train — you don't need any preposition.
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Now the means — the tool you do something with. What do you write with? Olovkom. Olovka drops -a and takes -om: Pišem olovkom. I write with a pen. Notice: in Serbian there's no word s here — the ending -om alone means by means of the pen. An instrument goes in the bare instrumental.
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Now the instrumental's second job — company. When you're WITH someone, you use the preposition s or sa and put the person in the instrumental: Idem sa sestrom. I'm going with my sister. Sestra becomes sestrom, with sa in front. Here the preposition IS required — because we're talking about company, not means.
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When s, when sa? Simple rule: use sa before a word starting with s, z, š or ž, so the sounds don't clash — hence sa sestrom, sa Žarkom. In all other cases plain s is enough.
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Back to means, because the instrumental also covers the WAY you do something. What do you cut bread with? Nožem: Sečem hleb nožem. I cut the bread with a knife. Nož takes -em instead of -om, because it ends in a soft consonant. But the meaning is the same — bare instrumental, a means with no preposition.
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Let's see the full forms so they stick. A hard stem takes -om: voz becomes vozom, kafa becomes kafom. A soft stem — one ending in j, č, ž, š or c — takes -em: nož becomes nožem, muž becomes mužem.
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Now the main trap — and the reason you're here. For transport and means you do NOT use a preposition. You say idem vozom, not idem s vozom. Keep the preposition s only for company, for people. The train isn't your company — the train is your means.
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To make it clear, here's a contrast. Putujem autobusom — that's a means, no preposition. But razgovaram sa vozačem — that's company, a person, so it takes sa. Same case, but the preposition depends on whether it's means or company.
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And a last example, joining both senses in one sentence. Means with no preposition, company with a preposition: Putujem autobusom sa prijateljem. I travel by bus with a friend. Autobusom — means, bare instrumental; sa prijateljem — company, with a preposition. Both in the instrumental, but only one takes sa.
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To recap. The instrumental answers by what? and with whom?. The ending is -om, and -em after soft consonants. Means and transport go with no preposition: idem vozom, pišem olovkom. Company takes the preposition s or sa: sa sestrom. Remember: the train is a means, not company.
