The glottal stop /ʔ/ is formed by the complete closure of the glottis (the space between the vocal cords), cutting off airflow, and then a sudden release of that closure. While English does not have a dedicated alphabet letter for this sound, speakers commonly use glottal stops in connected speech (for instance, in some dialects or informal speech, “button” may be pronounced [bʌʔn̩]). In clinical contexts, glottal stops are well known as compensatory articulation errors in individuals with velopharyngeal insufficiency or cleft palate: unable to build pressure in the oral cavity, a person might substitute a glottal stop for an oral stop consonant (saying “ʔame” for “came”). Glottal stop substitutions can significantly reduce intelligibility and voice quality, so speech therapy for cleft palate often targets eliminating glottal stops and replacing them with the appropriate oral consonants.
Janet Trost. “Articulatory additions to the classical description of the speech of persons with cleft palate.” Cleft Palate Journal 18, no. 3 (1981).
Anne K. Kummer. Cleft Palate and Craniofacial Anomalies: Effects on Speech and Resonance. 3rd ed. Cengage Learning, (2014).
