What is time?

Time is the fourth dimension woven into the fabric of spacetime. In physics (relativity), time is relative to the observer and cannot be separated from space – together they form a four-dimensional continuum. There's no absolute "flow"; clocks measure time based on physical processes, and time can dilate (run slower) near massive bodies or at high speed. Another angle: time's arrow is given by entropy – thermodynamics drives systems from ordered to disordered states, defining a direction for "future" versus "past." In everyday terms, time parametrizes change: events occur in a sequence we measure with clocks. But fundamentally, time is a coordinate in space-time, not an independent absolute.