The spelling of "Mervaille" can be explained using the IPA phonetic transcription. The word is pronounced as /mɛːvɑj/ in French, where the "e" represents the open mid-front unrounded vowel sound and the "ai" combination represents the diphthong /ɑj/. The letter "r" is silent in French, as usual. In English, "Mervaille" may be spelled as it is pronounced in French, or as "Marvel" with the "r" pronounced. It is important to note that the spelling of this word varies depending on the language in which it is used.