From previous grades, you know about different measurements such as measurement of height, weight, temperature, etc. Such quantities assume real numbers as their measure (with some unit of measurement). For example, the height of a tree is 5 m, the weight of a student is 45 kg, the temperature of a normal person is 36.5°C, etc. However, not all quantities assume only a single real number as their description. There are some quantities, called vectors, whose measures need to involve directions. These will be discussed in this unit.