vector

英['vektə] 美['vɛktɚ]

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

3. 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"