keyword

1. Indexing: Main or oft-repeated word (usually a noun) that is closely linked to, or describes or defines, a particular subject.

2. Database search: Word or phrase employed in narrowing down a database search. Keywords are central to a subject matter and, when used with Boolean search parameters ('And', 'Not', 'Or') work like a 'filter' to reduce the number of documents located (returned) by the search engine.

3. Internet marketing: Words or phrases 'sold' by the owner of a search engine (such as Google or Yahoo) to advertisers so that when a user specifies a keyword for a search the advertiser's ad automatically appears on top of the searched (returned) pages.