The spelling of the word "BETAPDH" can be explained using the International Phonetic Alphabet (IPA). The word is pronounced as /bɛtəpiːdiːeɪtʃ/ where "bet" is pronounced with a short "e" sound, "ap" and "dh" are pronounced as separate syllables with their respective sounds, and "i" is pronounced as a long "e". The letters "p," "d," and "h" represent their respective sounds, while "e," "a," and "t" have their own unique sounds in this context. Understanding the IPA phonetic transcription can help improve spelling and pronunciation skills.