Existence means presence, presence that’s detected and/or experienced :
The existent things in and around experienced by human senses; human being a living creature,itself means a form of existence
The existent things detected by things based on technology
It means ‘something’.
It is one existent form experiencing/detecting the same or a different existent form.
The universe-at-present is a vast collection of diverse existent forms and all that existent in and around us are in totality, the universe.When it is said that the universe includes all the existent,it goes without saying that it includes a percentage of existent that’s detected and/or experienced and a percentage of existent that is undetected,also.Of course,finding ‘existence’ depends on what we humans can experience with our senses and what our technology can detect.
Now,the universe means existence;does it include non-existence?does it include other-existence also? lets analyze->
All that we can experience and detect with the aid of technology does not mean we have captured all of the existent around us,near and far away.And also,when nothing is experienced,when nothing is detected it is not necessarily non-existence.
A)There might be many existent things which have not been experienced/detected by us either because they just cannot be experienced at all or there is a deficiency of technological advancement in our knowledge base which whenever filled up,enables us to experience those
B)it’s the other-existence
Only after ruling out A) and B) one can safely call it non-existence
So,does this universe include other-existence and non-existence in it’s existence ?
In short , an individual & the entire world around her[experienced,detected,undetected and hence unknown] is the Universe.