Vector (mathematics and physics)
WordNet
noun
(1) A variable quantity that can be resolved into components
(2) 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"
(3) A straight line segment whose length is magnitude and whose orientation in space is direction