Physical quantities can be classified into two categories: scalars and vectors.
Scalar
Distance, speed, mass, work and energy, time, temperature, volume, density, etc.
Scalar quantities have only magnitude and no direction. They are thus fully described by their numerical values (and units) alone. For example, 3 kg is 3 kg. There is no such thing as 3 kg eastward or westward.
Vector
Displacement, velocity, force, momentum etc.
Vector quantities on the other hand have both magnitude and direction. They thus require the specifications of a spatial direction in addition to a numerical value (and units). For example, 3 m s-1 northward is a different velocity than 3 m s-1 eastward.
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