腺 ㄒㄧㄢ ˋ xiàn 嘌 ㄆㄧㄠ ˋ piào 呤 ㄌㄧㄥ ˋ lìng adenine nucleotide (A, pairs with thymine T 胸腺嘧啶 in DNA and with uracil U 尿嘧啶 in RNA)