Consonants

In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the upper vocal tract, the upper vocal tract being defined as that part of the vocal tract that lies above the larynx. Consonants contrast with vowels.

Since the number of consonants in the world's languages is much greater than the number of consonant letters in any one alphabet, linguists have devised systems such as the International Phonetic Alphabet (IPA) to assign a unique symbol to each attested consonant. In fact, the Latin alphabet, which is used to write English, has fewer consonant letters than English has consonant sounds, so digraphs like "ch", "sh", "th", and "zh" are used to extend the alphabet, and some letters and digraphs represent more than one consonant. For example, many speakers are not aware that the sound spelled "th" in "this" is a different consonant than the "th" sound in "thing". (In the IPA they are transcribed and, respectively.)

Origin of the term
The word consonant comes from Latin oblique stem cōnsonant-, from cōnsonāns (littera) "sounding-together (letter)", a loan translation of Greek σύμφωνον sýmphōnon. As originally conceived by Plato, sýmphōna were specifically the stop consonants, described as "not being pronounceable without an adjacent vowel sound". Thus the term did not cover continuant consonants, which occur without vowels in a minority of languages, for example at the ends of the English words bottle and button. (The final vowel letters e and o in these words are only a product of orthography; Plato was concerned with pronunciation.)

However, even Plato's original conception of consonant is inadequate for the universal description of human language, since in some languages, such as the Salishan languages, stop consonants may also occur without vowels (see Nuxálk), and the modern conception of consonant does not require cooccurrence with vowels.

Consonantal features
Each consonant can be distinguished by several features:
 * The manner of articulation is the method that the consonant is articulated, such as nasal (through the nose), stop (complete obstruction of air), or approximant (vowel like).
 * The place of articulation is where in the vocal tract the obstruction of the consonant occurs, and which speech organs are involved. Places include bilabial (both lips), alveolar (tongue against the gum ridge), and velar (tongue against soft palate). Additionally, there may be a simultaneous narrowing at another place of articulation, such as palatalisation or pharyngealisation.
 * The phonation of a consonant is how the vocal cords vibrate during the articulation. When the vocal cords vibrate fully, the consonant is called voiced; when they do not vibrate at all, it's voiceless.
 * The voice onset time (VOT) indicates the timing of the phonation. Aspiration is a feature of VOT.
 * The airstream mechanism is how the air moving through the vocal tract is powered. Most languages have exclusively pulmonic egressive consonants, which use the lungs and diaphragm, but ejectives, clicks, and implosives use different mechanisms.
 * The length is how long the obstruction of a consonant lasts. This feature is borderline distinctive in English, as in "wholly" vs. "holy", but cases are limited to morpheme boundaries. Unrelated roots are differentiated in various languages such as Italian, Japanese and Finnish, with two length levels, "single" and "geminate". Estonian and some Sami languages have three phonemic lengths: short, geminate, and long geminate, although the distinction between the geminate and overlong geminate includes suprasegmental features.
 * The articulatory force is how much muscular energy is involved. This has been proposed many times, but no distinction relying exclusively on force has ever been demonstrated.

All English consonants can be classified by a combination of these features, such as "voiceless alveolar stop consonant". In this case the airstream mechanism is omitted.

Some pairs of consonants like p::b, t::d are sometimes called fortis and lenis, but this is a phonological rather than phonetic distinction.

Consonant as a symbol
The word consonant is also used to refer to a letter of an alphabet that denotes a consonant sound. Consonant letters in the English alphabet are B, C, D, F, G, H, J, K, L, M, N, P, Q, R, S, T, V, X, Z, and usually W and Y: The letter Y stands for the consonant in "yoke", and for the vowel  in "myth", for example; W is almost always a consonant except in rare words  (mostly loanwords from Welsh) like "crwth" "cwm".

Consonants and vowels
Consonants and vowels correspond to distinct parts of a syllable: The most sonorous part of the syllable (that is, the part that's easiest to sing), called the syllabic peak or nucleus, is typically a vowel, while the less sonorous margins (called the onset and coda) are typically consonants. Such syllables may be abbreviated CV, V, and CVC, where C stands for consonant and V stands for vowel. This can be argued to be the only pattern found in most of the world's languages, and perhaps the primary pattern in all of them. However, the distinction between consonant and vowel is not always clear cut: there are syllabic consonants and non-syllabic vowels in many of the world's languages.

One blurry area is in segments variously called semivowels, semiconsonants, or glides. On the one side, there are vowel-like segments which are not in themselves syllabic, but which form diphthongs as part of the syllable nucleus, as the i in English boil. On the other, there are approximants which behave like consonants in forming onsets, but are articulated very much like vowels, as the y in English yes. Some phonologists model these as both being the vowel /i/, so that the English word bit would phonemically be, beet would be , and yield would be phonemically. Similarly, foot would be, food would be , wood would be , and wooed would be. However, there is a (perhaps allophonic) difference in articulation between these segments, with the in  yes and  yield and the  of  wooed having more constriction and a more definite place of articulation than the  in  boil or  bit or the  of.

The other problematic area is that of syllabic consonants, that is, segments which are articulated as consonants but which occupy the nucleus of a syllable. This may be the case for words such as church in rhotic dialects of English, although phoneticians differ in whether they consider this to be a syllabic consonant,, or a rhotic vowel, : Some distinguish an approximant that corresponds to a vowel , for rural as  or ; others see these as the a single phoneme,.

Other languages utilize fricative and often trilled segments as syllabic nuclei, as in Czech and several languages in Congo and China, including Mandarin Chinese. In Mandarin, they are historically allophones of, and spelled that way in Pinyin. Ladefoged and Maddieson call these "fricative vowels" and say that "they can usually be thought of as syllabic fricatives that are allophones of vowels." That is, phonetically they are consonants, but phonemically they behave as vowels.

Many Slavic languages allow the trill and the lateral  as syllabic nuclei (see Words without vowels), and in languages like Nuxalk, it is difficult to know what the nucleus of a syllable is (it may be that not all syllables have nuclei), though if the concept of 'syllable' applies, there are syllabic consonants in words like  'seal fat'.

Common consonants
Many consonants are far from universal. For instance, nearly all Australian languages lack fricatives; a large percentage of the world's languages, for example Mandarin Chinese, lack voiced stops such as, , and. The most common consonants around the world are the three voiceless plosives, , and the two nasals ,.

Most languages, however, do include one or more fricatives, with being the most common, and a liquid consonant or two, with  the most common. The approximant is also widespread. However, even the basic five——are not universal. Several languages in the vicinity of the Sahara Desert, including Arabic, lack. Several languages of North America, such as Mohawk, lack both labials, and. Some West African languages, such as Ijo, lack on a phonemic level, but  does occur as an allophone of. A few languages on Bougainville Island and around Puget Sound, such as Makah, lack both nasals, and. The 'click language' Nǀu lacks, and colloquial Samoan lacks both alveolars, and. Xavante has no dorsal consonants whatsoever. However, nearly all other languages have at least one velar consonant: the few languages which do not have a simple have a consonant that is very similar. For instance, an areal feature of the Pacific Northwest coast is that historical *k has become palatalized in many languages, so that Saanich for example has and  but no plain.

The most frequent consonant (that is, the one appearing most often in speech) in many languages is.