Semivowels are vowel-like sounds that behave as consonants. Crosslinguistically, the palatal /j/ and labio-velar /w/ are the most common semivowels. Phonologically, these sounds are the non-syllabic counterparts of the high vowels /i/ and /u/: cf. ímen ‘we go’ vs. eîmi ‘I go’ and zugón ‘yoke’ vs. zeûgos ‘yoke of beasts’.

/w/, inherited from PIE, survived in Mycenaean and many first-millennium Greek di…