What we call a thing is for him a set of agitations of force, a group of activity or energy, a configuration of process or motion, and he calls such a bit of process an 'actual occasion'. We shall, however, for the sake of convenience, apply this term to things in general or objects of our experience. Sometimes, Whitehead calls these actual occasions 'drops of experience'. These names given to the material of the objects of common perception are to bring out that they are not isolated entities but currents of teleological process, continuous with all things in the universe. No part of the process can be abstracted from the others and studied correctly.
Every actual occasion involves every other, and to know any one is to know the whole universe.
Actual occasions are spatio-temporal aspects of process, a nexus of which we call an object. An object is nothing but a continuous process of actual occasions as we experience them in their externalised condition. There is no fixed object anywhere. An event is a series of actual occasions revealed in perception as demonstrated in a molecule for a few moments. Objects are more complex formulations of such events.