An intelligible form in philosophy refers to a form that can be apprehended by the intellect, in contrast to sense perception. According to Ancient and Medieval philosophers, the intelligible forms are the things by which we understand. These are Genera and species. Genera and species are abstract concepts, not concrete objects. For example, “animal”, “man” and “horse” are general terms that do not refer to any particular individual in the natural world. Only specific animals, men and horses exist in reality.