σ is pronounced [z] when followed by β, γ, δ, μ, ν, λ, ρ, μπ, ντ. This happens either within a word or across word boundaries

διάβασμα, σβούρα, τις ντομάτες, τους μπαμπάδες

Final ν followed by initial κ, π, τ makes them [b], [d], [g].

τον κήπο, την πόλη, τον τοίχο, τον ψαρά, τον ξένο

Within a word, there is a tendency to pronounce [i] followed by a vowel as a semivowel [j], [ç].

μάτια, ποιος [matça], [pços] βιάζομαι, παιδιά [vjazome], [peðja]

You can also read:The ‘να’ & the ‘ ότι’

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