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The first idea needed in describing the motion of an object is its position relative to some fixed reference point. This entails two ideas: the distance the object is away from the reference point, and also the direction relative to that reference point. For example, one could say that Toronto is about 3000 km east of Vancouver. Position, as defined above, is said to be a vector quantity, because it has both a magnitude, or size, (the distance) and a direction. Sometimes we wish to talk about the position of an object relative to its starting point at some initial time. This is called the displacement of the object.