Every Greek student I have taught has said some version of the same sentence in the first lesson: "I hear Serbian has seven cases." It is said the way you would mention a diagnosis. And it is the wrong thing to worry about.
You already have four. Nominative, genitive, accusative and vocative are alive and working in your Greek every single day. You don't think about them, you just use them — ο άνθρωπος, του ανθρώπου, τον άνθρωπο, άνθρωπε. That instinct is the expensive part of learning an inflected language, and you already paid for it as a child.
So what are the extra three?
Serbian adds the dative, the instrumental and the locative. Each one does a job that Greek does with a preposition instead.
- Dative — the receiver. Greek says στον φίλο μου; Serbian changes the ending: пријатељу.
- Instrumental — the tool or the company. Greek: με το αυτοκίνητο. Serbian: аутомобилом, one word.
- Locative — location, and only location. Greek: στην πόλη. Serbian: у граду.
Notice what these have in common. In Greek the meaning lives in the preposition; in Serbian it lives in the ending. You are not learning three new ideas. You are learning to move information you already express from one place in the sentence to another.
Where the real difficulty is
It isn't the number of cases. It is two other things, and neither one appears on the list students worry about.
1. Serbian has no articles at all
This is the single most persistent error I see in Greek speakers' Serbian, and it lasts long after the grammar is solid. Greek puts an article on almost everything. Serbian has none — not definite, not indefinite, nothing. Човек је дошао is both "the man came" and "a man came", and Serbian sorts out which one from context and word order.
For months your hand will reach for an article that isn't there. It is a harmless mistake in the sense that nobody will misunderstand you. It is also the thing that marks your speech as foreign long after your accent has settled.
2. Aspect, where Greek almost helps
Greek has perfective and imperfective, so the concept is not new. But the pairs don't line up. Serbian verbs mostly come in two separate forms — писати and написати, читати and прочитати — and choosing between them is a decision you make in every sentence, not a tense you conjugate into.
Your Greek instinct will get you to roughly the right answer most of the time. The remaining fraction is where the actual work is, and it takes real practice rather than a rule you can memorise.
The practical order I teach it in
Not all seven at once, and not in the order textbooks print them. What works:
- Nominative and accusative first, because they carry the majority of ordinary sentences.
- Locative next, since "where is it" comes up in the first week of any real conversation.
- Genitive after that, for possession and for the quantities that appear at every market stall.
- Dative and instrumental once you are speaking in full sentences and can feel the gap where they belong.
- Vocative last as a formal topic, though you will have been using it accidentally from day one.
By the time the last two arrive, they don't feel like new grammar. They feel like a tidier way to say something you were already saying the long way round.
The short version: seven is a number, not a difficulty rating. The cases are where your Greek helps you most. Spend the worry on the articles that aren't there.