Its position is not fixed, but varies in a complicated manner over time.

In general, when a rigid body moves, both its position and orientation vary with time.

Gravano's specific position within the family varied during 1986 and 1987.

These positions evolve and vary throughout the years to meet any needs.

These positions evolve and vary throughout the years as it is needed.

The position of the legs and free arm varies.

The Greeks understood that the position of the sun varies throughout the year.

These particular players' position and duties on the field vary from one offensive scheme to another.

The position varies considerably, but it always has one side to the wall.

Because the subject's position doesn't vary, it comes out sharp.