Probability distributions which represent the number of 'individuals' (such as particles) which fail to cross the speci?ed area containing the hazards of different kinds. For instance, the region might simply be a straight line containing a number of 'absorption' points. When the particle is moving along the line meets such a point, there is a probability p which will be absorbed by it. If it is absorbed it fails to make any more progress in it, but also the point is incapable of absorbing any further particles. When there is M active absorption in it.