A stop, plosive, or occlusive is a consonant sound produced by stopping the airflow in the vocal tract. The terms plosive and stop are usually used interchangeably, but they are not perfect synonyms. Plosives are stops with a pulmonic egressive airstream mechanism. The term is also used to describe oral (non-nasal) stops. Many use the term nasal continuant rather than nasal stop to refer to sounds like [n] and [m]. One should be aware that this article treats these "nasal continuants" as nasal stops.
All languages in the world have stops and most have at least [p], [t], [k], [n], and [m]. However, there are exceptions: Colloquial Samoan lacks the coronals [t] and [n], and the several North American languages, such as the northern Iroquoian languages, lack the labials [p] and [m]. Some of the Chimakuan, Salishan, and Wakashan languages near Puget Sound lack nasal stops [m] and [n], as does the Rotokas language of Papua New Guinea, and Eyak lacks both labials and nasals, [p], [m], [n]. 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 only one word with velar [k], but it has a nasal velar stop, [ŋ]. Ni‘ihau Hawaiian, which has /t/ for Standard Hawaiian /k/, can be analysed as having no velars, but in fact its /t/ and /n/ vary in pronunciation, [t]~[k] and [n]~[ŋ]. 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.
In the articulation of the stop, three phases can be distinguished:
Classification of stops
In aspirated stops, the voice onset (the time when the vocal cords begin to vibrate) comes perceivably later than the release of the stop. The duration between the release of the stop and the voice onset is called voice onset time (VOT). Tenuis stops have a voice onset time close to zero, meaning that voicing begins when the stop is released. Voiced stops have a negative voice onset time, meaning the voicing begins before the stop is released. A stop is called "fully voiced" if it is voiced during the entire occlusion. In English, however, initial voiced plosives like [b] or [d] are only partially voiced, meaning that voicing picks up sometime during the occlusion. Aspirated stops have a voice onset time greater than zero, so that there is a period of voiceless airflow (a phonetic [h]) before the onset of the vowel.
In most dialects of English, the final g in the word bag is likely to be fully voiced, while the initial b will be only partially voiced. 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. 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 a geminate or long stop, the occlusion lasts longer than in normal stops. In languages where stops are only distinguished by length (e.g. Arabic, Ilwana, Icelandic), the long stops may last up to three times as long as the short stops. Italian is well known for its geminate stop, 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 the geminate consonant, such as in the minimal pair 来た (kita), meaning came, and 切った (kitta) meaning cut (past).
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 tell 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 stops. Beware, however, that the terms fortis and lenis are poorly defined, and their meanings vary from source to source.
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 only used in languages where these sounds are phonemic, that is, not analyzed into sequences of plosive plus nasal stop.
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).
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.
[p], [t], [k] (aspirated word-initially, tenuis in clusters with s)
[b], [d], [g] (in most dialects: partially voiced word-initially, fully voiced intervocally)
[ʔ] (glottal stop, not as a phoneme in most dialects)
Published - October 2008
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