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⟩.