In a vector space formula_1 (with vectors being "arrows" with directions), the dimension of formula_1, also written as formula_3, is equal to the cardinality (or number of vectors) of a basis of formula_1 (a set which indicates how many unique directions formula_1 actually has). It is also equal to the number of the largest group of straight line directions of that space. "Normal" objects in everyday life are specified by three dimensions, which are usually called length, width and depth. Mathematicians call this concept Euclidean space.