### Vector

## Explanation

**CPER:** a vector is an abstract reference pointer, that indicates the direction of an evolutionary trend. Within the framework of the theory of CPER, a vector resembles the definition of a mathematical pointer or physical impulse, rather than of a biological carrier.

**Mathematics:** a vector is a geometric pointer-entity endowed with magnitude and direction as well as a positive-definite inner product. It is an element of an Euclidean vector space that is used to represent physical quantities that have both magnitude and direction (X, Y, Z), such as force, in contrast to scalar quantities, which have no direction. An inner product space is a vector space with an additional structure called an inner product. This additional structure associates each pair of vectors in the space with a scalar quantity known as the inner product of the vectors. Inner products allow the rigorous introduction of intuitive geometrical notions such as the length of a vector or the angle between two vectors. An inner product naturally induces an associated norm, thus an inner product space is also a normed vector space.

**Epidemiology:** a vector is a carrier-organism, often an invertebrate arthropod, that transmits a pathogen from reservoir to host.

**Molecular biology:** a vector is a carrier-vehicle used to transfer genetic material to a target cell, such as a plasmid vector.

## Linguistic derivation

The word *Vector* is derived from the Latin term *vehere*, which means "to carry".