The millisecond (ms) is a time unit equal to one-thousandth of a second, critical in computing, telecommunications, and scientific experiments where precise timing matters. Network latency, camera shutter speeds, and reaction time measurements all operate on the millisecond scale. One millisecond equals exactly 0.001 seconds, and the human eye can barely perceive changes faster than about 10 milliseconds.

The second (s) is the base unit of time in the International System of Units, defined by the vibration frequency of cesium-133 atoms. It serves as the foundation for all time measurements, from clocks and watches to GPS satellites and atomic physics. One second equals exactly 1,000 milliseconds and is divided into 60 seconds per minute.