Every particle of a body is pulled downward by gravity, so a body really experiences a large number of small, parallel weight forces distributed throughout its volume.

For calculation these many small forces can be replaced by a single equivalent force acting at one definite point, which simplifies problems of balance and stability.

That point is the centre of gravity: the point through which the entire weight of the object is taken to act.

Treating the whole weight as acting there lets us analyse tipping, balancing and support reactions as if one force pressed down at that spot.

It is not simply the lowest point of the object, because the balancing point usually lies inside the body, often near its middle.

Nor is it the point of maximum mass or the point where the object happens to be fixed or clamped; those describe different things entirely.

The defining idea is that the total weight is regarded as concentrated there.

It is the point where the entire weight of an object acts