Existing or occurring at the same time as something else; simultaneous.
From 'co-' (together) plus 'existent' (existing), based on Latin 'existens.' This adjective form emerged to describe things that happen or exist in parallel rather than in sequence.
Light and shadow are coexistent—you literally cannot have one without the other, which is why philosophers have used this relationship for thousands of years to explain how opposite things need each other to exist.
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