Secondary articulation

In phonetics, secondary articulation occurs when the articulation of a consonant is equivalent to the combined articulations of two or three simpler consonants, at least one of which is an approximant. The secondary articulation of such co-articulated consonants is the approximant-like articulation. It "colors" the primary articulation rather than obscuring it. Maledo (2011) defines secondary articulation as the superimposition of lesser stricture upon a primary articulation.

Types
There are several kinds of secondary articulation supported by the International Phonetic Alphabet:
 * Labialization is the most frequently encountered secondary articulation. For example, labialized has a primary velar plosive articulation,, with simultaneous -like rounding of the lips, thus the name. It is in contrast to the doubly articulated labial-velar consonant , which is articulated with two overlapping plosive articulations,  and.
 * Palatalization is perhaps best known from the Russian "soft" consonants like ), which has a primary alveolar plosive articulation,, with simultaneous -like (i.e. y-like) raising of the body of the tongue.
 * Labio-palatalization is simultaneous labialization and palatalization. It is found, for example, in the name Twi.
 * Velarization is the raising of the back of the tongue toward the velum, as in the English "dark" L,.
 * Pharyngealization is a constriction in the throat (pharynx) and is found in the Arabic "emphatic" consonants such as.
 * Glottalization involves action of the glottis in addition to the primary articulation of the consonant.

It can sometimes be difficult to distinguish primary and secondary articulation. For example, the alveolo-palatal consonants are sometimes characterized as a distinct primary articulation and sometimes as palatalization of postalveolar fricatives, equivalent to  or.

Transcription
The most common method of transcription in the IPA is to turn the letter corresponding to the secondary articulation into a superscript written after the letter for the primary articulation. For example, the w in ⟨kʷ⟩ is written after the k. This can be misleading, as it iconically suggests that the is released into a  sound, analogous to ⟨kˡ kⁿ⟩ ([k] with a lateral and nasal release), when actually the two articulations of  are generally pronounced more-or-less simultaneously. Secondary articulation often has a strong effect on surrounding vowels, and may have an audible realization that precedes the primary consonant, or both precedes and follows it. For example, will not generally sound simply like, but may be closer to  or even. For this reason, the IPA symbols for labialization and palatalization were for a time placed under the primary letter (e.g. ⟨k̫⟩ for and ⟨ƫ⟩ for ), and a number of phoneticians still prefer such unambiguous usage, with ⟨kʷ⟩ and ⟨tʲ⟩ used specifically for off-glides, despite the official policy of the IPA. In the official IPA there remains only an alternative symbol for velarization/pharyngealizaton that is superposed over the primary (e.g. ⟨ɫ⟩ for dark L), but that has font support for a limited number of consonants and is inadvisable for others, where it can be illegible. A few phoneticians use superscript letters for offglides and subscript letters for simultaneous articulation (e.g. ⟨tʲ⟩ vs ⟨tⱼ⟩).

There is a longstanding tradition in the IPA that one may turn any IPA letter into a superscript, and in so doing impart its features to the base consonant. For instance, would be an articulation of  that has qualities of. However, the features are not necessarily imparted as secondary articulation. Superscripts are also used iconically to indicate the onset or release of a consonant, the on-glide or off-glide of a vowel, and fleeting or weak segments. Among other things, these phenomena include pre-nasalization, pre-stopping , affrication , pre-affrication , trilled, fricative, nasal, and lateral release , rhoticization , and diphthongs. So, while ⟨ˠ⟩ indicates velarization of non-velar consonants, it is also used for fricative release of the velar stop (⟨ɡˠ⟩). Mixed consonant-vowels may indicate a transition: may be the allophone of  with the transition from  that identifies the consonant, while  may be the allophone of  before, or the formants of  anticipated in the.

The 2015 edition of the Extensions to the International Phonetic Alphabet formally advocates superscript letters for the first time since 1989, specifically for the release of plosives.