In phonetics, preaspiration (sometimes spelled pre-aspiration)^[1] is a period of voicelessness or aspiration preceding the closure of a voiceless obstruent,^[2] basically equivalent to an [h]-like sound preceding the obstruent. In other words, when an obstruent is preaspirated, the glottis is opened for some time before the obstruent closure.^[3] To mark preaspiration using the International Phonetic Alphabet, the diacritic for regular aspiration, ⟨ʰ⟩, can be placed before the preaspirated consonant. However, Ladefoged & Maddieson (1996:70) prefer to use a simple cluster notation, e.g. ⟨hk⟩ instead of ⟨ʰk⟩.

Preaspiration is comparatively uncommon across languages of the world,^[4] and is claimed by some to not be phonemically contrastive in any language.^[5] Ladefoged & Maddieson (1996) note that, at least in the case of Icelandic, preaspirated stops have a longer duration of aspiration than normally aspirated (post-aspirated) stops, comparable to clusters of [h]+consonant in languages with such clusters. As a result, they view preaspiration as purely a distributional feature, indistinguishable phonetically and phonologically from clusters with /h/, and prefer to notate preaspirated stops as clusters, e.g. Icelandic kappi /ˈkʰahpi/ "hero" rather than /ˈkʰaʰpi/.

A distinction is often made between so-called normative and non-normative preaspiration: in a language with normative preaspiration of certain voiceless obstruents, the preaspiration is obligatory even though it is not a distinctive feature; in a language with non-normative preaspiration, the preaspiration can be phonetically structured for those who use it, but it is non-obligatory, and may not appear with all speakers.^[6][7] Preaspirated consonants are typically in free variation with spirant-stop clusters, though they may also have a relationship (synchronically and diachronically) with long vowels or [s]-stop clusters.^[8]

Preaspiration can take a number of different forms; while the most usual is glottal friction (an [h]-like sound), the precise phonetic quality can be affected by the obstruent or the preceding vowel, becoming for example [ç] after close vowels;^[9] other potential realizations include [x]^[8] and even [f].^[10]

Preaspiration is very unstable both synchronically and diachronically and is often replaced by a fricative or by a lengthening of the preceding vowel.^[11]

Preaspiration is perhaps best known from North Germanic languages, most prominently in Icelandic and Faroese, but also some dialects of Norwegian and Swedish. It is also a prominent feature of Scottish Gaelic. The presence of preaspiration in Gaelic has been attributed to North Germanic influence.^[12] Within Northwestern Europe preaspiration is furthermore found in most Sami languages, except Inari Sami where it has been replaced by postaspiration.^[13] The historical relationship between preaspiration in Sami and North Germanic is disputed: there is general agreement of a connection, but not on whether it represents Sami influence in North Germanic,^{[14] [15]} North Germanic influence in Sami^[16] or parallel sprachbund influence in both languages.^[17]

Elsewhere in the world, preaspiration occurs in Halh Mongolian, Western Yugur, and in several American indigenous languages, including dialects of Hopi,^{[18][19][20][21]} Purepecha, and many languages of the Algonquian family (such as Cheyenne, Cree, Ojibwe, Fox, and Miami-Illinois).

Although distinguishing preaspirated consonants from clusters of /h/ and a voiceless consonant can be difficult, the reverse does not hold: there are numerous languages such as Arabic or Finnish where such clusters are unanimously considered to constitute consonant clusters.^{[citation needed]}

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• Prevoicing
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