A scalar quantity is a physical quantity that is described completely by a single numerical value (magnitude) along with a unit of measurement, but it has no direction. Scalars represent magnitude only and do not include any directional information
. Examples of scalar quantities include length, mass, charge, volume, time, speed, energy, and density
. For instance, saying "10 cm" or "5 kilograms" specifies a scalar quantity because it conveys only how much, not in which direction. In contrast to vectors, which have both magnitude and direction, scalars are unaffected by changes in coordinate systems like rotations or reflections and are described by real numbers in physics
. In summary, a scalar quantity:
- Is fully described by magnitude alone
- Has no direction
- Is represented by a real number and a unit
- Examples: mass, time, speed, temperature, volume
This distinguishes scalars from vectors, which require both magnitude and direction for their description
