"The World" versus "World"
"The world" suggests to me a thing with boundaries. It points to some outer limits of "the universe" and suggests something beyond. Nothingness? "The world" is a singularity that can be counted. So people speak of possible worlds, for example.
"World" is uncountable. It's what is, now. It's not only these things in my presence. It's what I am and what I'm experiencing. But really, what am I? I'm a configuration of world relating to itself and nothing more. I am world.
Separation is an act of imagination
Nothing can be separated from anything. If I take a nail and sterilize it and put it on a sterilized table in a white room and run tests on it, I have only distanced it from things things like bacteria and other nails. I can never separate it from world. I can only rearrange world.
Language -- whether everyday, philosophical, scientific, mathematical -- treats world as separable, isolatable. It's based on a suspension of other ways world operates. Language tends to treat "the world" like a box with a number of distinct things in it, then tries to figure out how they interact. Some would call it a lie.
The apparent gap between conscious human experience -- a system flooded with reductions, more so in powerful brains that read a lot -- and other aspects of world confounded Descartes. He called one the subject and the other the object. The subject was transcendent, outside of "the world." Christians believe in a soul.
The imagination works by way of reduction. So, for example, there are no apples, per se. There are configurations of world that the bit of body we call brain calls apples because that's how part of our body relates to other bits of world. The human body needs to change the apple into something else in order to bring it closer and manipulate it. Sometimes followed by action. This is a product of evolution. It's power-over, and power-over has survival advantages.