Scalars and Vectors:

In physics there are two basic classes of quantites. One class has a value and a unit attached to it. Quantities in this class are called scalars. Quantities from the other class also have directional information. They are called vectors.

Examples for scalars:
=> the temperature is a scalar: T = 20 °C on a sunny day in spring
=> the distance is a scalar: d = 160 km between two cities
=> the speed is a scalar: speed limit on most freeways is now 65 miles/hour

Examples for vectors:
=> displacement and velocity are vectors; for them the direction also matters.
=> force is a vector: F = 180 N in positive y-direction

The direction for vectors in 1-d is simply characterized by the sign.
In 2-d and 3-d, the direction information is either given by a pair or triplet of numbers, or graphically by an arrow. The numbers for the components of the vectors depend, however, on the coordinate system in which the vectors are described.