The spelling of the word "multitooth" is determined by its pronunciation. It is commonly pronounced as /mʌltiːtuːθ/, which indicates that the word is composed of several teeth or tooth-like structures. The prefix "multi-" denotes the presence of multiple elements, while the suffix "-tooth" implies that the elements in question resemble or function as teeth. Altogether, this results in a word that describes the existence of multiple tooth-like structures, such as those found in some fish species.