A universe is a single complete system of all that is - its a macro-organism endowed with an ecology of interdependent maintenance systems.

Most creatures can only be aware of their own universe, the one of ultimate importance to themselves. We do not know the number of parallel universes but we do know that at least seven of them are of importance to the human condition. These can best be described as alternative realities that exist simultaneously, quite apart from one another but related in that we exist in them all at once. Regarding the holistic nature of all creation words attributed to Gautama Buddha states, "Pluck a blade of grass and the universe shakes". We should perhaps be speaking about the Omniverse rather than the plural word universes. Now that this topic is as clear as it will be for me during this lifetime...I must move on;-)