Noun

(en noun)

Subject; theme; a category or general area of interest.

*{{quote-magazine, date=2013-08-03, volume=408, issue=8847, magazine=(The Economist)

, title= The machine of a new soul , passage=The yawning gap in neuroscientists’ understanding of their topic is in the intermediate scale of the brain’s anatomy. Science has a passable knowledge of how individual nerve cells, known as neurons, work. It also knows which visible lobes and ganglia of the brain do what. But how the neurons are organised in these lobes and ganglia remains obscure. Yet this is the level of organisation that does the actual thinking—and is, presumably, the seat of consciousness.}}

(Internet) Discussion thread.

(obsolete) An argument or reason.

* Bishop Wilkins

contumacious persons, who are not to be fixed by any principles, whom no topics can work upon

(obsolete, medicine) An external local application or remedy, such as a plaster, a blister, etc.

(Wiseman)

Noun

(en noun)

Any word used as the key to a code.

(information science) Any word used in a reference work to link to other words or other information.

(programming) A reserved word used to identify a specific command, function etc.

* 1982 , Popular Computing (volume 1, issues 9-12, page 113)

Each function has an entry address which must be quoted after the USR keyword .

(linguistics) Any word that occurs in a text more often than normal.