A constant which quantifies the dissociation between two atoms, molecules, or larger particles. This constant is used in the equation K=AB/AB, where K is the dissociation constant, A and B are the two substances which are dissociating from each other, and means "concentration of (in moles)."

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.