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".