Beekes - Etymological Dictionary of Greek

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PRE-GREEK LOANWORDS IN GREEK
PRE-GREEK LOANWORDS IN GREEK
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6.2. Long / short:
One may doubt whether Pre-Greek had a distinction of long and short vowels (see
Bl). We do find 'l and w, however, but not very often, and the latter has several
variants. On the other hand, the variations W / 0 and 'l / £ are not very frequent
(although in this case also the difference in timbre may have been important,
depending on the Greek dialect). Variation between long en short L and u is frequent,
especially in suffIxes: y8uov / yu8La, KU£