The spelling of the word "Hadden" can be explained using the IPA phonetic transcription. The first syllable is pronounced as "hæd" with the letter "a" sounding like the "a" in "cat." The second syllable is pronounced as "ən" with the "ə" sounding like the "uh" in "up." Therefore, the correct spelling of the word is "Hadden," not "Haddan" or "Haddun." It is important to pay attention to the phonetic sounds in a word to ensure correct spelling and pronunciation.