Plosives

In phonetics, a plosive, also known as an occlusive or an oral stop, is a stop consonant in which the vocal tract is blocked so that all airflow ceases. The occlusion may be done with the tongue (blade, , or body , ), lips , and lips and teeth &. Occlusives contrast with nasal stops, where the vocal tract is blocked but airflow continues through the nose, as in and, and with fricatives, where partial occlusion impedes but does not block airflow in the vocal tract.

Terminology
The terms occlusive, plosive, and stop are often used interchangeably, but they are not defined the same. Occlusives/plosives are oral stops, in contrast with nasal stops such as,. The ambiguity arises because the phrase nasal stop is frequently abbreviated to nasal, and oral stop to stop; in some ways nasal consonants behave more like sonorants than like oral stops, so the use of the term stop in reference to nasals may cause confusion.

The term stop refers to the stopping of the airflow, at least through the mouth. The term plosive derives from the plosive airflow which results when the occlusion of typical oral stops is released. The term occlusive refers to the occlusion of the vocal tract which stops the airflow. Plosive and occlusive are generally synonyms, though various authors may make idiosyncratic distinctions between them. In some cases, plosive refers exclusively to oral stops with outward airflow powered by the diaphragm, as in English. Occlusive may then be used as a cover term for plosives together with similar consonants with other airflow mechanisms, such as ejectives, implosives, and clicks, or as a cover term for plosives and affricates. In other cases, it is occlusive which is restricted to oral stops with outward airflow, while plosive covers implosives and clicks. In yet other cases, plosive means specifically the glottal stop, or the opposite, to oral stops excluding the glottal stop.

In Ancient Greek, occlusives were called áphōna (stoicheîa), which was translated into Latin as mūtae (cōnsōnantēs), and from there borrowed into English as mute. (Mute was sometimes used instead for voiceless consonants, whether occlusives or fricatives, a usage which was later replaced with surd, a term still occasionally seen in the literature.) Both the Latin and Greek terms sometimes referred to consonants in general, which ancient grammarians did not consider pronounceable on their own without vowels.

Common stops
All languages in the world have stops and most have at least the voiceless plosives, , and the nasals , and. However, there are exceptions: Colloquial Samoan lacks the coronals and, and several North American languages, such as the northern Iroquoian languages, lack the labials  and. In fact, the labial plosive is the least stable of the voiceless stops in the languages of the world, as the unconditioned sound change &rarr;  (&rarr;  &rarr; Ø) is quite common in unrelated languages, having occurred in the history of Classical Japanese, Classical Arabic and Proto-Celtic, for instance. Some of the Chimakuan, Salishan, and Wakashan languages near Puget Sound lack nasal stops and, as does the Rotokas language of Papua New Guinea. In some African and South American languages, nasal stops occur, but only in the environment of nasal vowels, and so are not distinctive. Formal Samoan has nasals and  but only one word with velar ; colloquial Samoan conflates these to. Ni‘ihau Hawaiian has for  to a greater extent than Standard Hawaiian, but neither distinguish a  from a. It may be more accurate to say that Hawaiian and colloquial Samoan do not distinguish velar and coronal stops than to say they lack one or the other.

Articulation
In the articulation of the plosive, three phases can be distinguished:
 * Catch: The airway closes so that no air can escape through the mouth (hence the name stop).
 * Hold or occlusion: The airway stays closed, causing a pressure difference to build up (hence the name occlusive).
 * Release or burst: The closure is opened. The released airflow produces a sudden impulse causing an audible sound, or burst (hence the name plosive).

In many languages, such as Malay and Vietnamese, final plosives lack a release burst, or have a nasal release. See Unreleased stop.

Nasal stops are somewhat similar. In the catch and hold, airflow continues through the nose; in the release, there is no burst, and final nasals are typically unreleased across most languages.

In affricates, the catch and hold are those of a plosive, but the release is that of a fricative. That is, affricates are plosive–fricative articulation contours.

Voice
Voiced stops are articulated with simultaneous vibration of the vocal cords, voiceless stops without. Plosives are commonly voiceless, whereas nasal stops are only rarely so.

Aspiration
In aspirated plosives, the vocal cords (or vocal folds) are abducted at the time of release. In a prevocalic aspirated plosive (a plosive followed by a vowel or sonorant), the time when the vocal cords begin to vibrate will be delayed until the vocal folds come together enough for voicing to begin, and will usually start with breathy voicing. The duration between the release of the plosive and the voice onset is called the voice onset time (VOT) or the aspiration interval. Highly aspirated plosives have a long period of aspiration, so that there is a long period of voiceless airflow (a phonetic ) before the onset of the vowel. In tenuis plosives, the vocal cords come together for voicing immediately following the release, and there is little or no aspiration (a voice onset time close to zero). In English, there may be a brief segment of breathy voice that identifies the plosive as voiceless and not voiced. In voiced plosives, the vocal folds are set for voice before the release, and often vibrate during the entire hold, and in English, the voicing after release is not breathy. A plosive is called "fully voiced" if it is voiced during the entire occlusion. In English, however, initial voiced plosives like or  may have no voicing during the period of occlusion, or the voicing may start shortly before the release and continue after release, though word-final plosives tend to be fully voiced: In most dialects of English, the final g in the bag is likely to be fully voiced, while the initial b will only be voiced during part of its occlusion. Initial voiceless plosives, like the p in pie, are aspirated, with a palpable puff of air upon release, while a plosive after an s, as in spy, is tenuous (unaspirated). When spoken near a candle flame, the flame will flicker more after the words par, tar, and car are articulated, compared with spar, star, and scar. In the common pronunciation of papa, the initial p is aspirated while the medial p is not.

Length
In a geminate or long consonant, the occlusion lasts longer than in simple consonants. In languages where plosives are only distinguished by length (e.g., Arabic, Ilwana, Icelandic), the long plosives may be held up to three times as long as the short plosives. Italian is well known for its geminate plosives, as the double t in the name Vittoria takes just as long to say as the ct does in English Victoria. Japanese also prominently features geminate consonants, such as in the minimal pair 来た kita 'came' and 切った kitta 'cut'.

Note that there are many languages where the features voice, aspiration, and length reinforce each other, and in such cases it may be hard to determine which of these features predominates. In such cases, the terms fortis is sometimes used for aspiration or gemination, while lenis is used for single, tenuous, or voiced plosives. Be aware, however, that the terms fortis and lenis are poorly defined, and their meanings vary from source to source.

Nasalization
Nasal stops are differentiated from oral stops only by a lowered velum that allows the air to escape through the nose during the occlusion.

Nasal stops are acoustically sonorants, as they have a non-turbulent airflow and are nearly always voiced, but they are articulatorily obstruents, as there is complete blockage of the oral cavity.

A prenasalized stop starts out with a lowered velum that raises during the occlusion. The closest examples in English are consonant clusters such as the [nd] in candy, but many languages have prenasalized stops that function phonologically as single consonants. Swahili is well known for having words whose spellings begin with mp or nd, like mtu, though truer prenasalized sounds like [mp] or [nd] do occur word-initially in other Bantu languages.

A postnasalized stop begins with a raised velum that lowers during the occlusion. This causes an audible nasal release, as in English sudden. Russian and other Slavic languages have words that begin with [dn], which can be seen in the name of the Dnieper River.

Note that the terms prenasalization and postnasalization are normally used only in languages where these sounds are phonemic: that is, not analyzed into sequences of plosive plus nasal stop.

Airstream mechanism
Stops may be made with more than one airstream mechanism. The normal mechanism is pulmonic egressive, that is, with air flowing outward from the lungs. All languages have pulmonic stops. Some languages have stops made with other mechanisms as well: ejective stops (glottalic egressive), implosive stops (glottalic ingressive), or click consonants (velaric ingressive).

Tenseness
A fortis stop (in the narrow sense) is produced with more muscular tension than a lenis stop (in the narrow sense). However, this is difficult to measure, and there is usually debate over the actual mechanism of alleged fortis or lenis consonants.

There are a series of stops in Korean, sometimes written with the IPA symbol for ejectives, which are produced using "stiff voice", meaning there is increased contraction of the glottis than for normal production of voiceless stops. The indirect evidence for stiff voice is in the following vowels, which have a higher fundamental frequency than those following other stops. The higher frequency is explained as a result of the glottis being tense. Other such phonation types include breathy voice, or murmur; slack voice; and creaky voice.

Examples
The following plosives have been given dedicated symbols in the IPA.


 * voiceless bilabial plosive
 * voiceless alveolar plosive
 * voiceless retroflex plosive
 * voiceless palatal plosive
 * voiceless velar plosive
 * voiceless uvular plosive
 * epiglottal plosive
 * glottal stop


 * voiced bilabial plosive
 * voiced alveolar plosive
 * voiced retroflex plosive
 * voiced palatal plosive
 * voiced velar plosive
 * voiced uvular plosive

English
,, (aspirated word-initially, tenuis in clusters with s)

,, (in most dialects: partially voiced word-initially, fully voiced intervocally)

(glottal stop, not as a phoneme in most dialects)