Semivowels

Semivowels (also called semiconsonants or glides, though these are now dispreferred) are non-syllabic vowels that form diphthongs with syllabic vowels. They may be contrasted with approximants, which are similar to but closer than vowels or semivowels, and behave as consonants. They are normally written by adding the IPA non-syllabic mark to a vowel symbol, but often for simplicity the vowel alone is written.

For example, the English word wow may be transcribed as (or abbreviated to ). Even though the and the  are both similar to the vowel, this transcription indicates that the former is considered to be a consonant, while the latter forms a diphthong with the preceding vowel. The approximant is more constricted and therefore more consonant-like than the semivowel. (Using for the diphthong rather than the  that one might expect is a minor phonetic point. See diphthong for details.)

Because they are so similar, the terms semivowel and approximant are often used interchangeably. In such usage, semivowels are defined as those approximants that correspond phonetically to specific close vowels. These are [j] corresponding to [i], [w] for [u], for [y], and  for. (See approximant for details.) However, languages such as Nepali and Samoan have additional semivowels that correspond to mid vowels such as and, which other than being non-syllabic are not at all consonant like.

Examples

 * English eye
 * English cow
 * Dutch ui "onion"
 * Samoan ’ai "probably"
 * Samoan ’ae "but"
 * Samoan ’auro "gold"
 * Samoan ao "a cloud"