Operation that assigns to every pair \(\left( \overrightarrow{u},\overrightarrow{v}\right)\) of vectors a new vector \(\left(\overrightarrow{u},\overrightarrow{v}\right)\) called the vector sum or the resultant vector.

The sum of two vectors is called the resultant. One way to find the resultant is by placing the initial point of the second vector at the terminal point of the first vector. The resultant is the vector from the initial point of the first vector to the terminal point of the second vector.

Therefore, if \(\overrightarrow{\textrm{AB}}\) and \(\overrightarrow{\textrm{BC}}\) are two vectors, then \(\overrightarrow{\textrm{AB}}+\overrightarrow{\textrm{BC}}=\overrightarrow{\textrm{AC}}\). This equality is also called the **Chasles relation**.