1) Actual Occasions/Entities; also known as “Final Realities” and “Res Verae” - This is a metaphysically primitive notion. It is a process of becoming rather than an enduring substance. They are the final, real things of which the world is made up or drops of experience that are complex, interdependent. This is similar to a Leignizian mod, except that a monad is windowless and nothing can pass through it, whereas an actual occasion is "all window." It is continually interpenetrated with other actual occasions.

Instead of the Aristotelian substance, which is indivisible, it is continually related to other actual occasions. The actual occasion is the inversion of Kant's philosophy. For Kant, the world emerges from the subject, who imposes his categories on the world. For Whitehead's actual occasion, the subject emerges from the world rather than creating it. This is very similar to Deleuze's project of wanting to determine the transcendental conditions of real, concrete experience rather than Kant's project of determining the transcendental conditions of possible experience.

2) Prehensions or Concrete Facts of Relatedness - The actual entity engages its world through "prehension." It is related to the more familiar word "apprehension." Both are derived from the Latin word for "to take." While apprehension refers to a subject taking hold of or grasping an object, Whitehead's neologism is meant to go beyond the subject/object distinction. There is a much more intimate relation of the subject to the object in Whitehead's prehension. Indeed, the object comes to be a constitutive component of the subject when the latter prehends the former.

There is an intense and real, ontological relatedness of the subject to the object rather than a mere sensory apprehension or cognitive comprehension. An event does not prehend itself. It prehends different things in diferent ways. The organism must select which data to prehend and which to exclude. In Whitehead's language, it is possible to engage in either positive or negative prehensions. In the case of a positive prehension, the subject enters into the concrescence of a novel occasion, internalizing the experience as part of its being, while excluding or negatively prehending what is not of interest of it, or that by which it is repulsed. In the case of a negative prehenson, the subject nonetheless preserves the prehended datum, bracketing it and keeping it as a reminder in its unconscious.

Thus, the individual makes a decision concerning which prehension to make the most of. This selection that is required, either a positive or negative prehension, is literally a "de-cision," which refers to a cutting off of certain experiences, making more readily available certain prehensions while bracketing others.

3) Subjective Forms or Private Matters of Fact - A manner of integrating prehensions. There are various subject forms or means by which data is prehended, such as consciousness, valuations, purposes or emotions. Once the decision concerning which prehensions to positively integrate have become made, a new event achieves "satisfaction," which is Whitehead's term for completion. This becomes new datum for prehensive activity.