A ‘glide’ is the transitional semivowel between /i/ and /u/ and a following mid or low vowel.
Although the term ‘glide’ can be used as a synonym of semivowel, in a narrower sense it describes the transitional semivowel between /i/ and /u/ and a following mid or low vowel, cf. French plier /pliˈ(j)e/. Glides have no phonological status in Ancient Greek and they are not usually represented in writing. However, glide-notation appears sometimes in early Greek inscriptions.
A [j] glide, spelled with iôta <i>, is found in the Ion. p.n. Diiophánēs …