The spelling of the word "Cetrexin" can be explained using the International Phonetic Alphabet (IPA) which is a system of phonetic notation based on the sounds of spoken language. The first syllable "Ce-" is pronounced as /sɛ/ with a short "e" sound, followed by the consonant cluster "tr" pronounced as /tr/. The second syllable "-trex-" is pronounced as /trɛks/, with a short "e" sound and the consonant cluster "x" pronounced like "ks". The final syllable "-in" is pronounced as /ɪn/ with a short "i" sound. Therefore, "Cetrexin" is spelled as /sɛtrɛksɪn/.