The word "Adenosus" is a scientific term used to describe a condition where a person's heart rate fails to increase with exercise. Its spelling can be explained using the International Phonetic Alphabet (IPA) transcription as [əˈdɛnoʊsəs]. The first syllable "a" is pronounced as "uh", followed by "d" and "e" pronounced as "duh" and "eh", respectively. The second syllable "no" is pronounced as "noʊ," and the final syllable "sus" is pronounced as "suh." Overall, the phonetic transcription helps in understanding the pronunciation and spelling of the word "Adenosus."