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 is composed of sounds like [ɹ] (as in rest) and semivowels like [j] and [w] (as in yes and west, respectively), as well as lateral approximants like [l] (as in less).
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: [ˈpi̯ɛˑde], and that of piano 'plan', 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. amplió ('he extended') y ɥ Labiopalatal French aigu ('sharp') vs. aiguille ('needle') ɯ ɰ** Velar Korean 음식 ('food') vs. 의사 ('doctor') u w Labiovelar Spanish continúo ('I continue') vs. continuó ('he continued') ɑ ʕ̞ Pharyngeal [example needed] ɚ ɻ Postalveolar, retroflex* North American English waiter vs. waitress
- ^* 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.
- ^** Because the vowels [i ɯ] are articulated with spread lips, spreading is implied for their approximant analogues, [j ɰ]. However, these sounds generally have little or no lip-spreading. The fricative letters with a lowering diacritic, ⟨ʝ˕ ɣ˕⟩, may therefore be justified for a neutral articulation between spread [j ɰ] and rounded [ɥ w].
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 they occur 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 is pronounced [futbo̞ˈlist], but маоїст ('Maoist'), with the same affix, is pronounced [mao̞ˈjist] with a glide. Dutch for many speakers has a similar process that extends to mid vowels:
- bioscoop → [bijɔskoːp] ('cinema')
- zee + en → [zeːjə(n)] ('seas')
- fluor → [flyɥɔr] ('fluorine')
- 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, where one of two adjacent vowels becomes non-syllabic; the 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, it 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 it is more frequently analyzed as velar (as in the table above), and Mapudungun may be another, with 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'). It has been noted that the expected symbols for the approximant correlates of [ɨ], [ʉ] are ⟨ɉ, ɥ̶⟩ or ⟨ɉ, w̶⟩.
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. Spanish can be analyzed as having a meaningful distinction between fricative, approximant, and intermediate /ʝ ʝ˕ j/. However, such frication is generally slight and intermittent, unlike the strong turbulence of fricative consonants.
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.
- 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⟩)
- breathy-voiced glottal approximant [ɦ]
- creaky-voiced glottal approximant [ʔ̞]
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, allowing free passage of air.
- voiced alveolar lateral approximant [l]
- retroflex lateral approximant [ɭ]
- voiced palatal lateral approximant [ʎ]
- velar lateral approximant [ʟ]
- uvular lateral approximant [ʟ̠]
Coarticulated approximants with dedicated IPA symbols
- labialized velar approximant [w] (a consonantal [u])
- labialized palatal approximant [ɥ] (a consonantal [y])
Voiceless approximants are not recognized by all phoneticians as a discrete phonetic category. There are problems in distinguishing voiceless approximants from voiceless fricatives.
Fricative consonants are generally said to be the result of turbulent airflow at a place of articulation in the vocal tract. However, an audible voiceless sound may be made without this turbulent airflow: Pike (1943) makes a distinction between "local friction" (as in [s] or [z]) and "cavity friction" (as in voiceless vowels like [ḁ] and [ɔ̥]). More recent research distinguishes between "turbulent" and "laminar" airflow in the vocal tract. It is not clear if it is possible to describe voiceless approximants categorically as having laminar airflow (or cavity friction in Pike's terms) as a way of distinguishing them from fricatives. Ball & Rahilly (1999) write that "the airflow for voiced approximants remains laminar (smooth), and does not become turbulent. Voiceless approximants are rare in the languages of the world, but when they do occur the airflow is usually somewhat turbulent." Audible voiceless sounds may also be produced by means of turbulent airflow at the glottis, as in [h]; in such a case, it is possible to articulate an audible voiceless sound without the production of local friction at a supraglottal constriction. Catford (1977) describes such sounds, but classes them as sonorants.
Voiceless approximants are rarely if ever distinguished phonemically from voiceless fricatives in the sound system of a language. Clark & Yallop (1995) discuss the issue and conclude "In practice, it is difficult to distinguish between a voiceless approximant and a voiceless fricative at the same place of articulation ... there is no evidence that any language in the world makes such a distinction crucial."
Disagreement over use of the term
Voiceless approximants are treated as a phonetic category by (among others) Ladefoged & Maddieson (1996), Catford (1977), and Bickford & Floyd (2006). However, the term voiceless approximant is seen by some phoneticians as controversial. It has been pointed out that if approximant is defined as a speech sound that involves the articulators approaching each other but not narrowly enough to create turbulent airflow, then it is difficult to see how a voiceless approximant could be audible. As John C. Wells puts it in his blog, "voiceless approximants are by definition inaudible ... If there's no friction and no voicing, there's nothing to hear." A similar point is made in relation to frictionless continuants by O'Connor (1973): "There are no voiceless frictionless continuants because this would imply silence; the voiceless counterpart of the frictionless continuant is the voiceless fricative." Ohala & Solé (2010) argue that the increased airflow arising from voicelessness alone makes a voiceless continuant a fricative, even if lacking a greater constriction in the oral cavity than a voiced approximant.
Ladefoged & Maddieson (1996) argue that Burmese and Standard Tibetan have voiceless lateral approximants [l̥] and Navajo and Zulu voiceless lateral fricatives [ɬ], but also say that "in other cases it is difficult to decide whether a voiceless lateral should be described as an approximant or a fricative". Asu, Nolan & Schötz (2015) compared voiceless laterals in Estonian Swedish, Icelandic, and Welsh and found that Welsh-speakers consistently used [ɬ], that Icelandic-speakers consistently used [l̥], and that speakers of Estonian Swedish varied in their pronunciation. They conclude that there is "a range of variants within voiceless laterals, rather than a categorical split between lateral fricatives and voiceless approximant laterals".
Occurrence in Western American English
(Not to be confused with 'nasal continuant', which is a synonym for nasal consonant)
- nasal palatal approximant [j̃]
- nasal labialized velar approximant [w̃]
- voiceless nasal glottal approximant [h̃]
What are transcribed as nasal approximants may include non-syllabic elements of nasal vowels or diphthongs.
- Ladefoged (1975:277)
- Martínez-Celdrán (2004:201), citing Ladefoged & Maddieson (1996)
- Martínez-Celdrán (2004), p. 201.
- Martínez-Celdrán (2004:201), pointing to Ladefoged (1964:25)
- Hall (2007), p. 316.
- 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 et al. (1999:283) citing Delattre & Freeman (1968), Zawadzki & Kuehn (1980), and Boyce & Espy-Wilson (1997)
- Both cited in Hamann (2003:25–26)
- John Esling (2010) "Phonetic Notation", in Hardcastle, Laver & Gibbon (eds) The Handbook of Phonetic Sciences, 2nd ed., p. 699.
- 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)" (PDF). Archived from the original (PDF) on 2011-07-20. Retrieved 2010-12-31.
- Listen to a recording Archived February 26, 2006, at the Wayback Machine
- Martin Ball & Joan Rahilly (2011) The symbolization of central approximants in the IPA. Journal of the International Phonetic Association. 41 (2), p. 231–237.
- Ball, Martin J.; Müller, Nicole (2011). Phonetics for communication disorders. Psychology Press. p. 70. ISBN 978-0-8058-5363-6.
- Boersma (1997:12)
- Martínez-Celdrán (2004:204)
- Martínez-Celdrán, E. (2004) "Problems in the classification of approximants". Journal of the International Phonetic Association, 34, 201–10.
- There have been repeated requests that the IPA created dedicated symbols for [β̞] and [ð̞] – typically modifications of the base letters such as turned ⟨β⟩ and ⟨ð⟩ or reversed ⟨β⟩ and ⟨ð⟩ – but so far the IPA has deemed that there is insufficient need for them.
- Ashby & Maidment (2005), pp. 56–7.
- Pike (1943), pp. 71, 138–9.
- Shadle (2000), pp. 37–8.
- Ball & Rahilly (1999), pp. 50–1.
- Catford (1977), pp. 122–3.
- Clark & Yallop (1995), p. 48.
- Akamatsu (1992), p. 30.
- Wells, J. C. (7 April 2009). "[h]: Fricative or approximant?". John Wells' Blog. Retrieved 23 December 2020.
- O'Connor (1973), p. 61.
- Ohala & Solé (2010), p. 43.
- Ladefoged & Maddieson (1996), pp. 198–9.
- Asu, Nolan & Schötz (2015), p. 5.
- Grønnum (2005), p. 154.
- Akamatsu, Tsutomu (1992), "A critique of the IPA Chart" (PDF), Contextos, X (19–20): 7–42, archived (PDF) from the original on 2022-10-09, retrieved 21 December 2020
- Asu, Eva Liina; Nolan, Francis; Schötz, Susanne (2015), "A comparative study of Estonian Swedish voiceless laterals: Are voiceless approximants fricatives?" (PDF), in Scottish Consortium for ICPhS 2015 (ed.), Proceedings of ICPhS 2015, University of Glasgow, ISBN 978-0-85261-941-4, archived (PDF) from the original on 2022-10-09
- Ashby, Michael; Maidment, John (2005), Introducing Phonetic Science, Cambridge, ISBN 0-521-00496-9
- Ball, Martin; Rahilly, Joan (1999), Phonetics: the Science of Speech, Arnold, ISBN 0-340-70010-6
- Bickford, Anita; Floyd, Rick (2006), Articulatory Phonetics (4th ed.), S.I.L. International, ISBN 1556711654
- 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 (6): 3741–3753, Bibcode:1997ASAJ..101.3741B, CiteSeerX 10.1.1.16.4174, doi:10.1121/1.418333, PMID 9193061
- Catford, J. C. (1988), A Practical Introduction to Phonetics, Oxford University Press
- Catford, J. C. (1977), Fundamental Problems in Phonetics, Edinburgh University Press, ISBN 0-85224-279-4
- Clark, John; Yallop, Colin (1995), An Introduction to Phonetics and Phonology (2nd ed.), Blackwell, ISBN 0-631-19452-5
- Delattre, P.; Freeman, D. C. (1968), "A dialect study of American R's by x-ray motion picture", Linguistics, 44: 29–68
- Grønnum, Nina (2005), Fonetik og fonologi, Almen og Dansk (3rd ed.), Copenhagen: Akademisk Forlag, ISBN 87-500-3865-6
- Hall, T. A. (2007), "Segmental features", in de Lacy, Paul (ed.), The Cambridge Handbook of Phonology, Cambridge University Press, pp. 311–334, ISBN 978-0-521-84879-4
- Hallé, Pierre A.; Best, Catherine T.; Levitt, Andrea; Andrea (1999), "Phonetic vs. phonological influences on French listeners' perception of American English approximants", Journal of Phonetics, 27 (3): 281–306, doi:10.1006/jpho.1999.0097
- Hamann, Silke (2003), The Phonetics and Phonology of Retroflexes, Utrecht: LOT, ISBN 90-76864-39-X[permanent dead link]
- 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 978-0-631-19815-4.
- Maddieson, Ian; Emmorey, Karen (1985), "Relationship between semivowels and vowels: Cross-linguistic investigations of acoustic difference and coarticulation", Phonetica, 42 (4): 163–174, doi:10.1159/000261748, PMID 3842771, S2CID 46872676
- Martínez-Celdrán, Eugenio (2004), "Problems in the classification of approximants", Journal of the International Phonetic Association, 34 (2): 201–210, doi:10.1017/S0025100304001732, S2CID 144568679
- 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, doi:10.1515/prbs.2004.005
- O'Connor, J. D. (1973), Phonetics, Penguin
- Ohala, John J.; Solé, Maria-Josep (2010), "Turbulence and Phonology" (PDF), in Fuchs, Susanne; Toda, Martine; Żygis, Marzena (eds.), Turbulent Sounds: An Interdisciplinary Guide, Berlin: De Gruyter Mouton, pp. 37–101, doi:10.1515/9783110226584.37, ISBN 978-3-11-022657-7, archived from the original (PDF) on 2021-06-03, retrieved 2021-06-03
- Pike, Kenneth (1943), Phonetics, University of Michigan Press
- Rubach, Jerzy (2002), "Against subsegmental glides", Linguistic Inquiry, 33 (4): 672–687, doi:10.1162/ling.2002.33.4.672, S2CID 57566358
- Saporta, Sol (1956), "A Note on Spanish Semivowels", Language, 32 (2): 287–290, doi:10.2307/411006, JSTOR 411006
- Shadle, Christine (2000), "The Aerodynamics of Speech", in Hardcastle, W. J.; Laver, J. (eds.), Handbook of Phonetic Sciences, Blackwell, ISBN 0-631-18848-7
- Trask, Robert L. (1996), A Dictionary of Phonetics and Phonology, London: Routledge
- Zawadzki, P. A.; Kuehn, D. P. (1980), "A cineradiographic study of static and dynamic aspects of American English /r/", Phonetica, 37 (4): 253–266, doi:10.1159/000259995, PMID 7443796, S2CID 46760239