The spelling of the word "Millifold" can be explained using IPA phonetic transcription. The word is pronounced as /mɪlɪfəʊld/. The first syllable "mil" is pronounced with a short "i" as in "ill". The second syllable "i" is pronounced with a long "i" as in "kite". The third syllable "fold" is pronounced with the "o" sound as in "old". Therefore, the spelling of "Millifold" can be remembered by breaking down its pronunciation into its individual sounds.