Illustrated Glossary of Organic Chemistry

Distribution coefficient (D): The ratio of solubility (or distribution) of a substance between two immiscible phases, usually two liquid phases. Also called the partition coefficient (P). The logarithm of the partition coefficient (logP) is used as a measure of hydrophobicity (lipophilicity) or hydrophilicity (lipophobicity).

--graphics to be added--  P or D = c1/c2