Classification of predators by the extent to which they feed on and interact with their prey is one way ecologists may wish to categorize the different types of predation. Instead of focusing on what they eat, this system classifies predators by the way in which they eat, and the general nature of the interaction between predator and prey species. Two factors are considered here: How close the predator and prey are (in the latter two cases the term prey may be replaced with host) and whether or not the prey are directly murdered by the predator is considered, with true predation and parasitoidism involving certain death.