The spelling of the word "ITOSI" can be explained using the International Phonetic Alphabet (IPA). It is pronounced as /iː.təʊ.siː/, with the first syllable "ee" as in "bee", the second syllable "toe" as in the body part, and the final syllable "see" as in the letter of the alphabet. The "o" in the second syllable represents the long vowel sound, and the "s" in the final syllable is pronounced as a voiceless "s" sound. Overall, the phonetic transcription helps to accurately depict the pronunciation and spelling of "ITOSI".