Debuccalization is a sound change in which a consonant becomes a glottal fricative or glottal stop. It is a common sound change which is also found in English. Debuccalization can be considered a weakening process.
Many speakers of English glottalize a /t/ when it is word-final and followed by a consonant and when it is followed by a syllabic nasal or liquid. This can occur in the following environments:
In Cockney English, an intervolic /t/ is replaced by a glottal stop, i.e., later, latest, city. In Canadian and American English, however, the /t/ is normally flapped here.
In Spanish, debuccalization also occurs. However, it is not a /t/ which becomes a glottal but rather an /s/. In many Spanish dialects such as those of Cuba, Venezuela and Panama, it is common for a syllable-final /s/ followed by a consonant to become an /h/. This happens in many words such as fresco (fresh), fiesta (party), and costa (coast).
Debuccalization is a common sound change. It can be classified as a subcategory of weakening, also known as lenition. With this sound change, the place of articulation shifts from the oral cavity to the glottis.