User:Grover cleveland/Semivowel

In phonetics and phonology, a semivowel is a sound that is phonetically equivalent to a vowel sound but functions as the syllable boundary rather than nucleus.

Classification
Semivowels form a subclass of approximants. Although "semivowel" and "approximant" are sometimes treated as synonmys, most authors agree that not all approximants are semivowels, although the exact details may vary from author to author. For example, Ladefoged and Maddieson consider that the labiodental approximant is not a semivowel,, while Martínez-Celdrán proposes that it should be considered a semivowel.

Types of semivowel
Martínez-Celdrán lists four semivowels according to what he calls "the established classification": they correspond to the four close cardinal vowel sounds:

In addition, some authors consider the rhotic approximants  to be semivowels corresponding to R-colored vowels such as. As mentioned above, the labiodental approximant is considered a semivowel in some treatments, but not others.

In some languages, such as Nepali, there exist semivowels correponding to mid-vowels. For example, colloquial Nepali has, which contrasts with the closer.

Contrast with vowels
Semivowels, by definition, contrast with vowels by being non-syllabic. In addition, they usually contrast at the phonetic level by being shorter than vowels. . In some languages, (Amharic, Yoruba, and Zuni), studies have shown that semivowels are produced with a narrower constriction in the vocal tract than their corresponding vowels. Nevertheless, in some cases semivowels may be effectively interchangeable with vowels. For example, the English word "fly" can be considered either as consisting phonetically of an open syllable ending in a diphthong, or as a closed syllable ending in a semivowel.

Contrast with fricatives/spirant approximants
According to the standard definitions, semivowels (such as ) contrast with fricatives (such as {IPA|[ʝ]}}) in that fricatives produce turbulence, while semivowels do not. In discussing Spanish, Martínez-Celdrán suggests setting up a third category of "spirant approximant", contrasting both with semivowel approximants and with fricatives. Though the spirant approximant is more constricted (having a lower F2 amplitude), longer, and unspecified for rounding (e.g. viuda 'widow' vs ayuda  'help'), the distributional overlap is limited. The spirant approximant can only appear in the syllable onset (including word-initially, where the semivowel never appears). The two overlap in distribution after and : enyesar  ('to plaster') aniego  ('flood') and, although there is dialectal and ideolectal variation, speakers may also exhibit other near-minimal pairs like abyecto ('abject') vs abierto ('opened'). One potential minimal pair (depending on dialect) is ya visto ('I already dress') vs y ha visto  ('and he has seen'). Again, this is not present in all dialects. Other dialects differ in either merging the two or in enhancing the contrast by moving the former to another place of articulation (e.g. ).

Contrast between close and mid semi-vowels
Samoan also contrasts close semivowels with mid ones:
 * Samoan ’ai ('probably')
 * Samoan ’ae ('but')
 * Samoan ’auro ('gold')
 * Samoan ao ('a cloud')

Romanian contrasts the diphthong with, a perceptually similar approximant-vowel sequence. The diphthong is analyzed as a single segment while the approximant-vowel sequence is analyzed as two separate segments. In addition to phonological justifications for the distinction (such as the diphthong alternating with in singular-plural pairs), there are phonetic differences between the pair:
 * has a greater duration than
 * The transition between the two elements is longer and faster for than  with the former having a higher F2 onset (i.e. greater constriction of the articulators).

Although a phonological parallel exists between and, the production and perception of phonetic contrasts between the two is much weaker, likely due to a lower lexical load for  (which is limited largely to loanwords from French) and a difficulty in maintaining contrasts between two back rounded glides in comparison to front ones.

Transcription
Semivowels may be transcribed in IPA either using dedicated symbols (j, w, etc.) or by adding the non-syllabic diacritic to a vowel sound (e̯, o̯, etc.)