What this means for learners
Greek and Slovene share 17 sounds — roughly 41% of Slovene's inventory overlaps with Greek. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 20 sounds found only in Slovene represent the greatest pronunciation challenge for Greek speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, Greek has 24 sounds not used in Slovene. Native Slovene speakers learning Greek will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.