vector
     n 1: a variable quantity that can be resolved into components
     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" [syn: {transmitter}]