Structural inherency: Laws or other barriers to the implementation of the plan. An example of this would be a plan under which the United States federal government imposes unilateral tariffs and quotas to prevent international trade. This plan is inherent because it goes against current World Trade Organization laws.
Gap inherency: Although the present system is aware that the problem exists, the steps in place fail to solve the existing harms. An example of this would be a plan removing all American forces from Afghanistan claiming that, although some troops are being removed from Afghanistan in the status quo, not all troops are being removed and the harms of military presence still exist.
Attitudinal inherency: Beliefs or attitudes which prevent the implementation of the plan. An example of this would be a plan under which the United States federal government eliminates all immigration laws concerning Mexico. This plan is inherent because the general attitude of Americans is that such increases in immigration would increase unemployment.
Existential inherency: Perhaps the strangest of the four, this claims that the plan won't be implemented simply because there is no reason it would be. An example of this would be a plan under which the United States federal government makes playing the board game Monopoly illegal. It may be possible to prove this plan to be a good idea; however, it is inherent and won't happen simply because it hasn't and probably won't.
Despite the classification of these four as the "main types" of inherency, the existence of other types are subject to theory (much like a substantial part of the lexicon for the event). In higher level policy debate inherency has become a non issue. There are some judges who will not vote on it, and negative teams do not run it often because it may contradict uniqueness arguments on disadvantages. However, inherency arguments are more likely to be run with a "Stocks Issues" judge who could hold that the absence of an inherent barrier is enough to merit an affirmative loss.