Vector

Part of speech: noun

Pronunciation: /ˈvɛktə/

Definitions

1. A quantity having both magnitude and direction, or an organism that transmits disease from one host to another
2. A mathematical object representing both direction and magnitude, or a carrier organism that spreads pathogens between hosts
3. A representation that combines both direction and size, or a living entity that facilitates the transfer of infectious agents

Etymology: The disease sense of "vector" is older than most people realise, and it sits oddly beside the mathematical one. Latin "vector" simply meant "carrier" or "transporter", from "vehere", "to carry". English took the word directly from Latin as a learned borrowing, so its roots lie in the everyday business of moving goods and people, the same root that gives us "vehicle". The disease meaning reflects the idea of something that carries a pathogen from one host to another, such as a mosquito carrying malaria. From there the word has spread into looser uses. The sense for a person or entity that passes along an urban legend or other meme derives directly from that disease meaning, as a carrier passing something on. The mathematical sense came later and from a different direction. Irish mathematician and astronomer William Rowan Hamilton coined it in 1846, using the idea of something that "carries" a point from one position to another. The same Latin word thus gave English both a biological term and a term for quantities with direction and magnitude.

Synonyms: direction, path, course, trajectory, line