A vector, in its simplest form, is a mathematical entity defined by both magnitude and direction. In geometry and natural sciences, vectors often represent directed segments in Euclidean space or on a plane.

The triangle rule for vector addition:

The parallelogram rule for the addition of vectors:

The unit vectors directed along the coordinate axes Ox and Oy are denoted as i and j, respectively.

If a = x * i + y * j, then the numbers x and y are called vector coordinates.