vector

a variable quantity that can be resolved into components

a straight line segment whose length is magnitude and whose orientation in space is direction

any agent (person or animal or microorganism) that carries and transmits a disease; "mosquitos are vectors of malaria and yellow fever"; "fleas are vectors of the plague"; "aphids are transmitters of plant diseases"; "when medical scientists talk about vectors they are usually talking about insects"

(genetics) a virus or other agent that is used to deliver DNA to a cell