The letters Waw و and Yaa ي are also called Leen letters because they are flexible letters. They blend with the vowel sound from the previous letter, allowing two vowel sounds.
waw leen Soft was
When a letter having Fathah - is followed by letter ‘Ya’, the vowel sound starts off as an ‘a’ sound and ends as an ‘i’ sound (rhymes with Ice). it produces "ay sound (some cases "ai"). This is called ‘Ya Leen’ or ‘soft Ya