In medicine, both ancient and modern, a dyscrasia is any of various disorders. The word has ancient Greek roots meaning "bad mixture". The concept of dyscrasia was developed by the Greek physician Galen (129–216 AD), who elaborated a model of health and disease as a structure of elements, qualities, humors, organs, and temperaments (based on earlier humorism). Health was understood in this perspective to be a condition of harmony or balance among these basic components, called eucrasia. Disease was interpreted as the disproportion of bodily fluids or four humours: phlegm, blood, yellow bile, and black bile. The imbalance was called dyscrasia. In modern medicine, the term is still occasionally used in medical context for an unspecified disorder of the blood, such as a plasma cell dyscrasia.