metabolism; the biological process of converting substances into energy or new tissue as old ones are broken down, often used as a short form for 新陈代谢 xīn​chén​dài​xiè

the natural purpose or activity of something, such as a biological or chemical process; often used as a suffix to mean "-ation" or "-ing" as in 消化 xiāo​huà plus this word for "digestion"