Let’s use a knife as an example. Its properties include its length, weight, and sharpness. These properties characterize the more or less enduring states of the knife and are therefore always actual: at any one point in time a knife is either sharp or blunt. A sharp knife, on the other hand, also has capacities, like its capacity to cut. Unlike sharpness, the capacity to cut need not be actual, if the knife is not presently cutting something, and may never become actual if the knife is never used. And when a capacity does become actual it is never as an enduring state but as a more or less instantaneous event. Moreover, this event is always double, to cut-to be cut, because a capacity to affect must always be coupled to a capacity to be affected: a particular knife  may be able to cut through bread, cheese, paper, or even wood, but not through a solid block of titanium. This implies that while properties are finite and may be put into a closed list, capacities to affect may not be fully enumerated because they depend on a potentially infinite number of capacities to be affected. Thus, a knife may not only have a capacity to cut but also a capacity to kill, if it happens to interact with a large enough organism with differentiated organs, that is, with an entity having the capacity to be killed. (DeLanda 2010:70-1)
DELANDA, Manuel. 2010. Deleuze: History and Science. New York: Atropos Press.