Metaphysics
Etymology
The name is almost an accident. From Greek "meta ta physika," “the [writings] after the Physics” — the label an early editor, traditionally Andronicus of Rhodes in the first century BCE, gave to the works Aristotle placed after his “Physics.” Readers later reinterpreted “meta” as “beyond,” yielding the modern sense of what lies beyond the physical.
noun · /met-uh-FIZ-iks/
The branch of philosophy that investigates the fundamental nature of reality — being, time, cause, identity, and what underlies the physical world.
What it names
A handle for the questions science assumes but cannot itself answer: why there is something rather than nothing, what makes a thing the same thing over time, whether cause is real.
Example
Once the argument turned to whether time itself is real, we had drifted from physics into metaphysics.
Related idea
Ontology, the study of what exists, is really a department within metaphysics, which ranges more widely over cause, time, and possibility as well.