Radicals are sounds produced in the back of the throat. They are divided into two categories: pharyngeals and epiglottals. Pharyngeals/epiglottals are commonly found in North Africa/Middle East (Arabic and related languages) and in British Columbia, in the Salishan languages. Pharyngeal plosives are thought to be impossible. Very few languages contrast epiglottal and pharyngeal consonants.
The pharyngeals possible are the voiceless pharyngeal fricative and the voiced pharyngeal fricative, actually an approximant. The epiglottals possible are the epiglottal plosive, the voiceless epiglottal fricative, the voiced epiglottal fricative, actually an approximant, the epiglottal trill, and the epiglottal flap, which is not known to occur in any language.
Ingressive and mixed airstreams
An ingressive airstream is what is generated when, instead of air flowing out, air flows in. In an mixed airstream consonant, air is pushed both in and out of the mouth, by two different methods. Ingressive consonants can be either voiced or voiceless. There are three types of ingressive consonants: Pulmonic ingressive, glottalic ingressive and clicks. Mixed airstreams are found in implosive consonants and some clicks. In order of commoness, they are ejectives, implosives, and clicks and glottal ingressives. Pulmonic ingressives are not known to be phonemic in any language.
There are a large number of ejective consonants. The most common is k'. They are considered glottalic egressives, where the airflow is caused by the glottis moving upward rapidly, causing pressure in the oral cavity to increase rapidly. They are slightly more common than implosive consonants according to WALS, occuring in 95 languages, out of the 576 languages listed. It is sometimes postulated to exist in PIE, but such theories are usually discredited. All ejectives are unvoiced and oral (not nasal nor glottal). They are represented with an apostrophe after the letter in question. Semivowel and trill ejectives are postulated to exist, but are not found in languages, presumably because of the difficulty in pronouncing such ejectives. All unvoiced oral obstruents can be ejectives, but bilabial ejectives are rare. If a sound is not in the voiceless inventory of a language, it is unlikely that it will have the corresponding ejective.
The implosive consonants are as follows. They are found in 76 out of 576 languages listed according to WALS. They are mainly found in sub-Saharan Africa and South East Asia. Most "pulmonic" stops are lightly imploded. They are made of
- b - ɓ
- d - ɗ
- ɟ - ʄ
- g - ɠ
This appears in english as the "glug-glug" onomatopoeia
Although affricate implosives are theoretically possible, they are not found, presumably due to the difficulty in pronouncing and distinguishing it.
Glottalic ingressive consonants are articulated similarly, except that they are voiceless. They are significantly rarer than implosive consonants. They are usually shown as an implosive consonant with a voiceless diacritic. Occasionally they are shown with a upward left hook and the corresponding voiceless consonant like ƙ (which in some dialects, is also the glug-glug onomatopoeia). These are extremely rare
Lingual ingressives, or clicks, are the next most common, centered around the Khoisan languages in Africa. Khoisan is not a genetic family, but a wastebasket taxon with most click languages of Africa. Clicks can be articulated in a variety of ways. They can be nasalized and can be pulmonically voiced, unvoiced, or a whole litany of contours. Clicks come in several main POAs, bilabial, dental, alveolar, retroflex, and palatal. In addition there is a percussive click, pronounced by the tongue smacking the bottom of the mouth. The percussive click only occurs in a cluster with alveolars in the only language where it is attested, the Sandawe language.
Click consonants are famous to the Western world mainly because of the 1980s movie, The Gods Must Be Crazy, in which the main character is a member of a tribe that communicates only in clicks. No language has been found that communicates in only clicks, however. || is a dental click and ! is an alveolar click