I’d like to know if there are differences between the byzantine pronunciation (used in churches) and the modern greek pronunciation. They seem to be the same, but someone has said to me they are different.
Do you mean with words that are spelt the same way in the religious texts as well as in Modern Greek? In that case, there are some differences. For example, in the church pronunciation, the various ways of spelling the sound are always pronounced as a full vowel, which may not be the case in the modern language when they occur before another vowel – ἀλήθεια will have 4 syllables in church but has 3 in modern Greek. Another thing is that in combinations like μπ, ντ, γκ, γγ, the first letter is always pronounced in church, while it may or may not be in the modern language – πέντε is always [pende] in church, but can be [pede] in everyday life.
On second thought, it’s not really a different pronunciation – the actual values given to letters are the same. It’s not as if υ and οι were pronounced like French u, for example.