⁹A vector is a mathematical quantity possessing both a magnitude and a direction. Force (F), displacement (x), and velocity (v) are all vector quantities. Some physical quantities such as temperature (T), work (W), and energy (E) possess magnitude but no direction. We call these directionless quantities “scalar.” It would make no sense at all to speak of a temperature being “79 degrees Celsius due North” whereas it would make sense to speak of a force being “79 Newtons due North”. Physicists commonly use a little arrow symbol over the variable letter to represent that variable as a vector, when both magnitude and direction matter. Thus represents a force vector with both magnitude and direction specified, while plain F merely represents the magnitude of that force without a specified direction. A “dot-product” is one way in which vectors may be multiplied, and the result of a dot-product is always a scalar quantity.