The spelling of the word "petrella" can be understood using the International Phonetic Alphabet (IPA). The first syllable "pe" is pronounced as "pɛ", with the letter "e" sounding like "eh" in "bed". The second syllable "tre" is pronounced as "tɹe", with the letter "e" sounding like "ey" in "grey". The final syllable "lla" is pronounced as "lə", with the letter "a" sounding like the schwa sound in "sofa". Overall, the IPA transcription for "petrella" is /pɛtɹelə/.