Vector
Etymology
From Latin “vector” (a carrier or conveyor), from “vehere” (to carry). The mathematical sense of a directed quantity is 19th-century; the same root gives “disease vector,” a carrier that conveys a pathogen.
noun · /VEK-ter/
A quantity that has both a size and a direction, such as velocity or force.
What it names
It captures that many real quantities are not just “how much” but “how much, which way” — and the direction changes everything.
Example
Two forces of equal size that are vectors pointing in opposite directions cancel out, while the same magnitudes aligned would double.
Related idea
A vector differs from a plain scalar number by carrying direction; speed is a scalar (just a magnitude), whereas velocity is a vector, which is why an object moving at steady speed around a curve is still accelerating.
noun · /VEK-ter/
An organism, such as a mosquito or tick, that carries and transmits a disease-causing agent from one host to another.
What it names
The carrier rather than the germ, and explains why public health so often fights the messenger — draining swamps, spraying nets — instead of the pathogen itself.
Example
Mosquitoes are the primary vector for malaria, so control efforts target the insects, not just the parasite.
Related idea
Unlike the virus it carries — the germ that actually does the harm — the vector is only the courier, which is why public health so often fights the messenger by draining swamps and spraying nets.
noun · /VEK-ter/
In computer security, the route or method an attacker uses to break into a system.
What it names
It gives a single name to the ‘way in’ — the specific channel of an attack, such as a phishing email or an open port — letting defenders reason about paths, not just damage.
Example
The phishing email was the attack vector that let ransomware onto the network.
Related idea
A zero-day is one specific unpatched flaw an attacker can use; the attack vector is the broader path or technique that carries the attack in — which is exactly what a firewall tries to block.