Scalar (physics)

A scalar is a physical quantity whose value is specified by magnitude alone, without direction. Examples include mass, temperature, and energy.

Vector (physics): A physical quantity with magnitude and direction, such as displacement or velocity. Vectors differ from scalars because their direction is part of the quantity.
Coordinate transformation: A rule for expressing coordinates or components in a different coordinate system. A scalar's value stays unchanged under a change of coordinates.
Mass: A measure of a body's inertia and, in gravitational theories, its role as a source of gravity. Mass is a familiar scalar quantity used to describe matter.
Pseudoscalar: A quantity that behaves like a scalar under proper rotations but changes sign under reflections. It resembles a scalar under rotations but fails to remain unchanged under reflection.
Physical quantity: A property of a system or phenomenon that can be measured and expressed numerically with a unit. Scalars are one kind of measurable physical quantity.
Scalar field: A function assigning a scalar value to every point in a space or region. It extends a single scalar quantity across space, as temperature does in a room.
Temperature: A physical quantity that characterizes thermal state and determines the direction of heat transfer. Temperature assigns a scalar value to thermal state at a point or for a system.
Vector component: A numerical coordinate representing one part of a vector relative to a chosen basis. A component may look like a scalar number but changes when the basis changes.
SI base unit: One of seven units in the International System of Units from which other SI units are defined. Scalar measurements use units such as the kilogram and kelvin.
Scalar multiplication: Multiplication of a vector or other mathematical object by a scalar. It shows how scalar values can rescale directional quantities without supplying direction themselves.

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