- Mathematics.
- a quantity possessing both magnitude and direction, represented by an arrow the direction of which indicates the direction of the quantity and the length of which is proportional to the magnitude.
- such a quantity with the additional requirement that such quantities obey the parallelogram law of addition.
- such a quantity with the additional requirement that such quantities are to transform in a particular way under changes of the coordinate system.
- any generalization of the above quantities.
- the direction or course followed by an airplane, missile, or the like.
- Biology.
- an insect or other organism that transmits a pathogenic fungus, virus, bacterium, etc.
- any agent that acts as a carrier or transporter, as a virus or plasmid that conveys a genetically engineered DNA segment into a host cell.
- an array of data ordered such that individual items can be located with a single index or subscript.
- to guide (an aircraft) in flight by issuing appropriate headings.
- to change direction of (the thrust of a jet or rocket engine) in order to steer the craft.
- 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
