[med-student]

What does dissociation rate constant practically mean in antibody affinity assays? For example Kd = 5nM/L

[Babcock_Hall]

It is a forum policy that you must show some attempt or thinking before we can help you.  I might be able to get you started, however.  Your title says "dissociation rate constant" but the number you quote looks to be a thermodynamic dissociation constant, often given the symbol K_d.  A good place to start is to clarify which you mean, and what is the context of the question.