a variable quantity, such as force, that has magnitude and direction and can be resolved into components that are odd functions of the coordinates. It is represented in print by a bold italic symbol: F or ̄F

an element of a vector space

an organism, esp an insect, that carries a disease-producing microorganism from one host to another, either within or on the surface of its body

an agent, such as a bacteriophage or a plasmid, by means of which a fragment of foreign DNA is inserted into a host cell to produce a gene clone in genetic engineering

the course or compass direction of an aircraft

any behavioural influence, force, or drive

to direct or guide (a pilot, aircraft, etc) by directions transmitted by radio

to alter the direction of (the thrust of a jet engine) as a means of steering an aircraft