Tell a Serbian speaker that they already know several hundred Greek words and they will not believe you. Then you list the first ten and the objection changes from "that is not true" to "wait, that one is Greek?"
Serbian has been taking vocabulary from Greek for more than a millennium, through three quite different doors: the Church, the Ottoman centuries, and the international scientific vocabulary that every European language shares. The words came in at different times and by different routes, and they behave differently as a result.
The church layer
This is the oldest and the most direct. Serbian literacy arrived through Byzantium, and Church Slavonic took liturgical vocabulary from Greek more or less wholesale. These words have been in the language for eight hundred years and nobody thinks of them as foreign.
- икона ← εικόνα
- анђео ← ἄγγελος
- јеванђеље ← εὐαγγέλιον
- манастир ← μοναστήριον
- монах, калуђер ← μοναχός, καλόγερος
- поп ← παπάς
- ђакон ← διάκονος
- литургија ← λειτουργία
- епископ, патријарх ← ἐπίσκοπος, πατριάρχης
- тамјан ← θυμίαμα
- ћелија ← κελλίον — a monk's cell first, a biological cell much later
And one that always gets a reaction: ђаво, from διάβολος. So is ђак, a pupil, which goes back to διάκος — originally someone in minor church orders, since for centuries the people who could read were the people in church.
The everyday layer
These arrived later and by messier routes — some directly, many through Turkish during the Ottoman period, which is why the Greek and Serbian forms sometimes differ more than you would expect. Etymologists argue about individual cases; the Greek origin is not in doubt, only the road taken.
- кревет ← κρεβάτι
- кутија ← κουτί
- хартија ← χαρτί
- сунђер ← σφουγγάρι
- пита ← πίτα
- тигањ ← τηγάνι
- фуруна ← φούρνος
- патос ← πάτος
- мермер ← μάρμαρον
- босиљак ← βασιλικός — literally "royal", which is a nicer name for basil than either language deserves
- трпеза ← τράπεζα
The three that surprise everyone
If you want to convince a sceptical Serb in under a minute, use these.
јефтин
From εὐθηνός. One of the most ordinary adjectives in the language, used forty times a day, and entirely Greek. Nobody expects this one.
хиљада
From χιλιάδα. Serbian counts to a thousand in Greek — which becomes obvious the moment you notice that Croatian uses the Slavic tisuća instead. The two languages took different words for the same number, and Serbian took the Greek one.
Half the names in the phone book
Јован, Петар, Ђорђе, Никола, Василије, Стефан, Јелена, Катарина — Greek in origin, every one, arriving with Christianity. A Serbian Ђорђе and a Greek Γιώργος are the same name wearing different clothes, and both celebrate on the same saint's day.
The international layer
This one is not really borrowing from Greek so much as both languages drawing on the same well, usually through Latin, German or French. It still means the words are free for you.
математика, физика, историја, музика, политика, демократија, телефон, биологија, аутоматски, кризa, систем, проблем, програм — and several hundred more. A Serbian speaker reading a Greek newspaper headline about politics or science recognises far more than they expect.
Where the meanings drifted
Shared origin does not mean shared meaning, and this is where the free vocabulary turns into a trap.
- трпеза / τράπεζα — in Serbian, a table laid for a meal, with a faintly ceremonial ring to it. In modern Greek, a bank. Same word, and you will not get far in a Greek high street asking where the nearest трпеза is.
- хартија / χαρτί — Greek uses it for paper in general, including the sheet you write a shopping list on. Serbian keeps it narrower and slightly more formal; the everyday word is папир.
- Register in general — several borrowed words are neutral in one language and archaic, poetic or regional in the other. That is not predictable from the form. It has to be learned word by word.
The practical takeaway for a Serbian speaker learning Greek: you start with several hundred words already half-known, which is a real advantage in the first months. Use it — and then be suspicious of it from about month three onwards, because by then the words that look familiar are precisely the ones most likely to be doing a different job.
One last thing worth saying: the traffic went both ways. Greek has taken Slavic vocabulary too, particularly place names across northern Greece and a scattering of rural and agricultural terms. Neither language has been sitting still, and neither has been alone.