What is the term for the three-letter consonant clusters at the start of many Greek words (like pter- in pteron), which were pronounced as two separate consonants in Classical times?

• A prothetic clusters
• B initial consonant clusters ✓
• C syllabic onset
• D digraph combinations

Greek tolerates complex word-initial consonant clusters (pt-, kt-, mn-, pn-, tm-, etc.) that are difficult for non-native speakers; in Ancient Greek both consonants were pronounced, but in Modern Greek the first often becomes silent.