Abaza, like its relatives in the family of Northwest Caucasian languages, is highly agglutinative and has a large consonantal inventory (63 phonemes) coupled with a minimal vowel inventory (two vowels). It is very closely related to Abkhaz, but it preserves a few phonemes which Abkhaz lacks, such as a pharyngeal voiced fricative. Work on Abaza has been carried out by W. S. Allen, Brian O'Herin, and John Colarusso.