Glide Details
[ya]

[high front] ----> [low back]
(offset transition of [i])
[ay]

[low back] ----> [high front]
(onset transition of [i])
  1. semi-vowel: roughly one-half of vowel
  2. glide: transition (movement)
  3. less energy, shorter duration
  4. nonsyllabic
  5. vowel in consonant environment