|Manners of articulation|
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Approximants are speech sounds that involve the articulators approaching each other but not narrowly enough nor with enough articulatory precision to create turbulent airflow. Therefore, approximants fall between fricatives, which do produce a turbulent airstream, and vowels, which produce no turbulence. This class of sounds includes lateral approximants like [l] (as in less), non-lateral approximants like [ɹ] (as in rest), and semivowels like [j] and [w] (as in yes and west, respectively).
Some approximants resemble vowels in acoustic and articulatory properties and the terms semivowel and glide are often used for these non-syllabic vowel-like segments. The correlation between semivowels and vowels is strong enough that cross-language differences between semivowels correspond with the differences between their related vowels.
Vowels and their corresponding semivowels alternate in many languages depending on the phonological environment, or for grammatical reasons, as is the case with Indo-European ablaut. Similarly, languages often avoid configurations where a semivowel precedes its corresponding vowel. A number of phoneticians distinguish between semivowels and approximants by their location in a syllable. Although he uses the terms interchangeably, Montreuil (2004:104) remarks that, for example, the final glides of English par and buy differ from French par ('through') and baille ('tub') in that, in the latter pair, the approximants appear in the syllable coda, whereas, in the former, they appear in the syllable nucleus. This means that opaque (if not minimal) contrasts can occur in languages like Italian (with the i-like sound of piede 'foot', appearing in the nucleus: [ˈpi̯eˑde], and that of piano 'slow', appearing in the syllable onset: [ˈpjaˑno]) and Spanish (with a near minimal pair being abyecto [aβˈjekto] 'abject' and abierto [aˈβi̯erto] 'opened').
Approximant-vowel correspondences Vowel Corresponding
Example i j Palatal Spanish amplío ('I extend') vs. ampliamos ('we extend') y ɥ Labiopalatal French aigu ('sharp') vs. aiguille ('needle') ɯ ɰ Velar Korean 쓰다 sseuda [s͈ɯda] ('to wear') vs. 씌우다 ssuiuda [s͈ɰiuda] ('to make s.o. wear') u w Labiovelar Spanish actúo ('I act') vs. actuamos ('we act') ɚ ɻ Retroflex* American English waiter vs. waitress ɑ ʕ̞ Pharyngeal [example needed]
- ^* Because of the articulatory complexities of the American English rhotic, there is some variation in its phonetic description. A transcription with the IPA character for an alveolar approximant ([ɹ]) is common, though the sound is more postalveolar. Actual retroflexion may occur as well and both occur as variations of the same sound. However, Catford (1988:161f) makes a distinction between the vowels of American English (which he calls "rhotacized") and vowels with "retroflexion" such as those that appear in Badaga; Trask (1996:310), on the other hand, labels both as r-colored and notes that both have a lowered third formant.
In articulation and often diachronically, palatal approximants correspond to front vowels, velar approximants to back vowels, and labialized approximants to rounded vowels. In American English, the rhotic approximant corresponds to the rhotic vowel. This can create alternations (as shown in the above table).
In addition to alternations, glides can be inserted to the left or the right of their corresponding vowels when occurring next to a hiatus. For example, in Ukrainian, medial /i/ triggers the formation of an inserted [j] that acts as a syllable onset so that when the affix /-ist/ is added to футбол ('football') to make футболіст 'football player', it's pronounced [futˈbo̞list] but маоїст ('Maoist'), with the same affix, is pronounced [ˈmao̞jist] with a glide. Dutch has a similar process that extends to mid vowels:
- bioscoop → [bijɔskoːp] ('cinema')
- zee + en → [zeːjə(n)] ('seas')
- fluor → [flyɥɔr] ('fluor')
- reu + en → [røɥə(n)] ('male dogs')
- Rwanda → [ruʋandɐ] ('Rwanda')
- Boaz → [boʋas] ('Boaz')
Non-high semivowels also occur. In colloquial Nepali speech, a process of glide-formation occurs, wherein one of two adjacent vowels becomes non-syllabic; this process includes mid vowels so that [dʱo̯a] ('cause to wish') features a non-syllabic mid vowel. Spanish features a similar process and even nonsyllabic /a/ can occur so that ahorita ('right away') is pronounced [a̯o̞ˈɾita]. It is not often clear, however, whether such sequences involve a semivowel (a consonant) or a diphthong (a vowel), and in many cases that may not be a meaningful distinction.
Although many languages have central vowels [ɨ, ʉ], which lie between back/velar [ɯ, u] and front/palatal [i, y], there are few cases of a corresponding approximant [ ȷ̈]. One is in the Korean diphthong [ ȷ̈i] or [ɨ̯i], though this is more frequently analyzed as velar (as in the table above), and Mapudungun may be another: It has three high vowel sounds, /i/, /u/, /ɨ/ and three corresponding consonants, /j/, and /w/, and a third one is often described as a voiced unrounded velar fricative; some texts note a correspondence between this approximant and /ɨ/ that is parallel to /j/–/i/ and /w/–/u/. An example is liq /ˈliɣ/ ([ˈliɨ̯]?) ('white').
Approximants versus fricatives 
In addition to less turbulence, approximants also differ from fricatives in the precision required to produce them. When emphasized, approximants may be slightly fricated (that is, the airstream may become slightly turbulent), which is reminiscent of fricatives. For example, the Spanish word ayuda ('help') features a palatal approximant that is pronounced as a fricative in emphatic speech. However, such frication is generally slight and intermittent, unlike the strong turbulence of fricative consonants.
Because voicelessness has comparatively reduced resistance to air flow from the lungs, the increased air flow creates more turbulence, making acoustic distinctions between voiceless approximants (which are extremely rare cross-linguistically) and voiceless fricatives difficult. This is why, for example, the voiceless labialized velar approximant [w̥] (also transcribed with the special letter ⟨ʍ⟩) has traditionally been labeled a fricative, and no language is known to contrast it with a voiceless labialized velar fricative [xʷ]. Similarly, Standard Tibetan has a voiceless lateral approximant, [l̥], and Welsh has a voiceless lateral fricative [ɬ], but the distinction is not always clear from descriptions of these languages. Again, no language is known to contrast the two. Iaai is reported to have an unusually large number of voiceless approximants, with /l̥ ɥ̊ w̥/.
For places of articulation further back in the mouth, languages do not contrast voiced fricatives and approximants. Therefore the IPA allows the symbols for the voiced fricatives to double for the approximants, with or without a lowering diacritic.
Occasionally, the glottal "fricatives" are called approximants, since [h] typically has no more frication than voiceless approximants, but they are often phonations of the glottis without any accompanying manner or place of articulation.
Central approximants 
- bilabial approximant [β̞] (usually transcribed ⟨β⟩)
- labiodental approximant [ʋ]
- dental approximant [ð̞] (usually transcribed ⟨ð⟩)
- alveolar approximant [ɹ]
- retroflex approximant [ɻ ] (a consonantal [ɚ])
- palatal approximant [j] (a consonantal [i])
- velar approximant [ɰ] (a consonantal [ɯ])
- uvular approximant [ʁ̞] (usually transcribed ⟨ʁ⟩)
- pharyngeal approximant [ʕ̞] (a consonantal [ɑ]; usually transcribed ⟨ʕ⟩)
- epiglottal approximant [ʢ̞] (usually transcribed ⟨ʢ⟩)
Lateral approximants 
In lateral approximants, the center of tongue makes solid contact with the roof of the mouth. However, the defining location is the side of the tongue, which only approaches the teeth.
- alveolar lateral approximant [l]
- retroflex lateral approximant [ɭ]
- palatal lateral approximant [ʎ]
- velar lateral approximant [ʟ]
- velarized alveolar lateral approximant [ɫ] or [lˠ]
Coarticulated approximants with dedicated IPA symbols 
- labialized velar approximant [w] (a consonantal [u])
- labialized palatal approximant [ɥ] or [jʷ] (a consonantal [y])
Voiceless approximants 
Voiceless approximants are rarely distinguished from voiceless fricatives. Some of them are:
- voiceless alveolar lateral approximant [l̥]
- voiceless palatal approximant [j̊]
- voiceless labialized palatal approximant [ɥ̊] or [j̊ʷ]
- voiceless labialized velar approximant [ʍ] or [w̥]
- voiceless glottal approximant [h]
- voiceless nasal glottal approximant [h̃]
See also 
|Look up approximant in Wiktionary, the free dictionary.|
- Ladefoged (1975:277)
- Martínez-Celdrán (2004:201), citing Ladefoged & Maddieson (1996)
- Martínez-Celdrán (2004:201)
- Martínez-Celdrán (2004:201), pointing to Ladefoged (1964:25)
- Ladefoged & Maddieson (1996:323), citing Maddieson & Emmorey (1985)
- Rubach (2002:680), citing Kawasaki (1982)
- Montreuil (2004:104)
- Saporta (1956:288)
- Martínez-Celdrán (2004:202)
- Ladefoged & Maddieson (1996:323)
- Hallé, Best & Levitt (1999:283) citing Delattre & Freeman (1968), Zawadzki & Kuehn (1980), and Boyce & Espy-Wilson (1997)
- Both cited in Hamann (2003:25–26)
- Rubach (2002:672)
- Rubach (2002:675–676)
- Rubach (2002:677–678)
- There is dialectal and allophonic variation in the realization of /ʋ/. For speakers who realize it as [ʋ], Rubach (2002:683) postulates an additional rule that changes any occurrence of [w] from glide insertion into [ʋ].
- Ladefoged & Maddieson (1996:323–324)
- Martínez-Celdrán, Fernández-Planas & Carrera-Sabaté (2003:256–257)
- Ahn & Iverson (2006)
- Listen to a recording
- Boersma (1997:12)
- Martínez-Celdrán (2004:204)
- Blevins (2006:13)
- Ohala (1995:8)
- Ladefoged & Maddieson (1996:326)
- Blevins, Juliette (2006), "New perspectives on English sound patterns: "natural" and "unnatural" in evolutionary phonology", Journal of English Linguistics 34: 6–25, doi:10.1177/0075424206287585
- Boersma, Paul (1997), "Sound change in functional phonology", Functional Phonology: Formalizing the Interactions Between Articulatory and Perceptual Drives, The Hague: Holland Academic Graphics
- Boyce, S.; Espy-Wilson, C. (1997), "Coarticulatory stability in American English /r/", Journal of the Acoustical Society of America 101: 3741–3753, doi:10.1121/1.418333, PMID 9193061
- Delattre, P.; Freeman, D.C. (1968), "A dialect study of American R's by x-ray motion picture", Linguistics 44: 29–68
- Hallé, Pierre A.; Best, Catherine T.; Levitt; Andrea (1999), "Phonetic vs. phonological influences on French listeners' perception of American English approximants", Journal of Phonetics 27: 281–306, doi:10.1006/jpho.1999.0097
- Hamann, Silke (2003). The Phonetics and Phonology of Retroflexes. Utrecht. ISBN 90-76864-39-X.
- Kawasaki, Haruko (1982), An acoustical basis for universal constraints on sound sequences (doctoral dissertation), University of California, Berkeley
- Ladefoged, Peter (1964). A Phonetic Study of West African Languages. Cambridge: Cambridge University Press.
- Ladefoged, Peter (1975). A Course in Phonetics. New York: Harcourt Brace Jovanovich.
- Ladefoged, Peter; Maddieson, Ian (1996). The Sounds of the World's Languages. Oxford: Blackwell. ISBN 0-631-19814-8.
- Maddieson, Ian; Emmorey, Karen (1985), "Relationship between semivowels and vowels: Cross-linguistic investigations of acoustic difference and", Phonetica 42: 163–174
- Martínez-Celdrán, Eugenio (2004), "Problems in the classification of approximants", Journal of the International Phonetic Association 34 (2): 201–210, doi:10.1017/S0025100304001732
- Martínez-Celdrán, Eugenio; Fernández-Planas, Ana Ma.; Carrera-Sabaté, Josefina (2003), "Castilian Spanish", Journal of the International Phonetic Association 33 (2): 255–259, doi:10.1017/S0025100303001373
- Montreuil, Jean-Pierre (2004), "From velar codas to high nuclei: phonetic and structural change in OT", Probus 16: 91–111
- Rubach, Jerzy (2002), "Against subsegmental glides", Linguistic Inquiry 33 (4): 672–687
- Ohala, John (1995), "Phonetic explanations for sound patterns: Implications for grammars of competence", Proceedings of the 16th International Congress of Phonetic Sciences 2, Stockholm, pp. 52–59
- Saporta, Sol (1956), "A Note on Spanish Semivowels", Language 32 (2): 287–290, doi:10.2307/411006
- Trask, Robert L. (1996). A Dictionary of Phonetics and Phonology. London: Routledge.
- Zawadski, P.A.; Kuehn, D.P. (1980), "A cineradiographic study of static and dynamic aspects of American English /r/", Phonetica 37: 253–266, doi:10.1159/000259995, PMID 7443796