The spelling of the word "Grenon" can be explained through its International Phonetic Alphabet (IPA) transcription. The first syllable, "gre", is pronounced with the phonemes /ɡ/ and /ɹ/, which represent the voiced velar plosive and the voiced alveolar approximant respectively. The second syllable, "non", is pronounced with the phonemes /n/ and /ɑː/, which represent the nasal consonant and the open back unrounded vowel respectively. Therefore, the correct phonetic spelling of "Grenon" is /ˈɡɹɛnɑn/.