The voiced velar stop is a type of consonantal sound, used in some spokenlanguages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨ɡ⟩, and the equivalent X-SAMPA symbol is g. Strictly, the IPA symbol is the so-called single-story G , though the double-story G is considered an acceptable alternative. The Unicode character "Latin small letter G" (U+0067) renders as either a single-story G or a double-story G depending on font, while the character "Latin small letter script G" (U+0261) is always a single-story G, but is generally available only in fonts with the IPA Extensions character block.
Of the six stops that would be expected from the most common pattern world-wide—that is, three places of articulation plus voicing ([p b, t d, k ɡ])—[p] and [ɡ] are the most frequently missing, being absent in about 10% of languages that otherwise have this pattern. Absent stop [p] is an areal feature (see also Voiceless bilabial stop). Missing [ɡ], on the other hand, is widely scattered around the world. (A few languages, such as Modern Standard Arabic, are missing both.) It seems that [ɡ] is somewhat more difficult to articulate than the other basic stops. Ian Maddieson speculates that this may be due to a physical difficulty in voicing velars: Voicing requires that air flow into the mouth cavity, and the relatively small space allowed by the position of velar consonants means that it will fill up with air quickly, making voicing difficult to maintain in [ɡ] for as long as it is in [d] or [b]. This could have two effects: [ɡ] and [k] might become confused, and the distinction is lost, or perhaps a [ɡ] never develops when a language first starts making voicing distinctions. (with uvulars, where there is even less space between the glottis and tongue for airflow, the imbalance is more extreme: Voiced [ɢ] is much rarer than voiceless [q]). Many Indo-Aryan languages, such as Hindustani, have a two-way contrast between aspirated and plain [ɡ].
The voiced pre-velar stop or voiced pre-velar plosive is a consonant occurring in standard Modern Greek. It's equally valid to use the term post-palatal instead of pre-velar, since they're essentially equivalent.
The voiced post-velar stop or voiced post-velar plosive is a consonant occurring in Australian English. It's equally valid to use the term pre-uvular instead of post-velar, since they're essentially equivalent.
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