Let U (the universe) denote a set of all possible spacetime events. An event E (whether a wave or a particle) is any subset of U. To say that the event E has occurred, is to say that a measurement done is a subset of two mutually exclusive disjointed sets of exact position in space [math]S(\psi)[/math] and time interval of zero [math]T(\phi)[/math] such that at the least the event E is associated with an element of S and an element of T.

[math] E=\psi \cup \phi [/math] and [math] \psi \cap \phi = 0 [/math]

In classical mechanics, an event E is denoted by the union of more than one spacetime points, which are all mutually exclusive disjointed points.

[math]E=\psi_1 \cup \phi_1 \cup \psi_2 \cup \phi_2 \cup \psi_3 \cup \phi _3 \cup …[/math]

and the intersections of all points in S and T is the empty set

[math]\psi_1 \cap \phi_1 \cap \psi_2 \cap \phi_2 \cap \psi_3 \cap \phi _3 \cup…=0 [/math]

However, for quantum mechanics and Einstein’s relativities (SR and GR), the intersections cannot be identically zero.