Vector
The vector x (lowercase, bold, by convention; equivalently, 
) can be thought of as a point in n-dimensional space. Conventionally, we mean column-vector when we say vector. The transpose of a column vector is a row vector with the same number of elements, arranged in a single row.
Scalar product of vectors
Also known as the dot product, the scalar product is defined for two vectors of equal length. The result of the operation is a scalar value and is obtained by summing over the products of the corresponding elements of the vectors. Thus, given vectors x and y:
The dot product xTy is given as:
