The spelling of the word "Substile" can be a bit confusing for English speakers. In IPA (International Phonetic Alphabet), its transcription goes like this: sʌbstaɪl. The "s" sound is followed by a schwa sound, then a "b" and "s" sound. The second syllable starts with a "t" followed by the "ai" diphthong and the "l" sound. The word is pronounced as "sub-stail." Understanding IPA can help to correctly spell and pronounce tricky words like this one.