[not an acronym] name for Greek symbol representing the ratio of the circumference of a circle to its diameter; approximately 3.1416[没有名字的缩写)希腊符号代表比例的圆周一圈,它的直径约3.1416; phosphatidylinositol磷脂酰肌醇 plaque index菌斑指数 premature infant早产儿