Semivowels (or glides) are the consonantal realizations of vowels. Only the high vowels (i, u and sometimes y) can be realized as semivowels, i.e. as j, w and h. Many languages show productive alternations between i and j, u and w, i.e. when the vowel /i/ occurs outside the nucleus of the syllable (e.g. because of morphology), it is relaised as /j/.