The word "koralline" is spelled with two L's, despite its pronunciation sounding like there's only one. The IPA phonetic transcription for "koralline" is /kəˈrælɪn/, which breaks down the word into its individual sounds. The first syllable "ko" is pronounced with a short "uh" sound followed by a "k" sound, while the second syllable "ral" is pronounced with a short "a" sound followed by an "l" sound. The last syllable "line" is pronounced with a short "i" sound followed by an "n" sound. Therefore, although it may seem counterintuitive, "koralline" is spelled with double "L's."