The approximate acceleration due to gravity at Earth's surface is 9.8 m/s². This means that, ignoring air resistance, a freely falling object's downward velocity increases by about 9.8 metres per second every second.
The value is an approximation because Earth's gravity is not identical everywhere. Earth rotates, is slightly flattened at the poles, and has uneven distributions of rock and mass. Gravity is therefore weaker near the equator and stronger near the poles. Elevation also matters: moving farther from Earth's center slightly reduces the acceleration.
Scientists often use the conventional standard gravitational acceleration, written gₙ, as 9.80665 m/s². It was adopted internationally in 1901 as a reference value, not as the exact measurement at one particular location. Introductory physics commonly rounds it to 9.8 m/s², or sometimes 10 m/s² for quick mental calculations.
Gravity should not be confused with weight. Gravity is an acceleration or field strength, measured in m/s² or equivalently N/kg. Weight is the force produced when an object's mass interacts with that field, so the same object weighs slightly differently at different locations.