Semivowels

Semivowels are sound that have both features of vowels and consonants. Phonetically, they are vowels, because they are pronounced with no air obstruction, but phonologically, they are consonants, because they are not nucleuses of syllables. To be really different from vowels, semivowels must come before or after a vowel and be short, otherwise, they are normal, syllabic vowels.

Semivowels in Orish
In Orish, when semivowels come where there is no vowel before or after them, they are neutralized into normal syllabic vowels. That also affects the spellings, the letter Y is replaced with the letter I and the letter W is replaced with the letter U.
 * Y - represents the palatal approximant, which is a non-syllabic high front unrounded vowel.
 * W - represents the labiovelar approximant, which is a non-syllabic high back rounded vowel.