Is a search engine a database?

Speaking strictly in terms of technical vocabulary Words, a search engine is a program that reads a database and returns results based on the contents of the database.

A search engine cannot return results unless the database stores the results.

Both of the answers above are true in a limited sense. google, however, is a widely known search engine that creates its own database. A search engine creates an index of terms that are ususally stored with or without documents in a database of some sort. Many search engines do the same as google: they create a database, index, search and retrieve the data that has been indexed and stored in some collection or data-base.

Some search engines also have indexes persoanal names or tags and/or a database of knowledge in the form of Word senses, dictionaries, thesauri, morphemes, phonemes, sentenances, and; in the semantic web, the web itslef is the database and the search engine reads distributed files (called RDF).

Some semantic search engines, such as Readawre, also do filtering, classification and provide a range of text analytics for a range of unstructed texts or messages (stored as independent files on disk). And many semantic search engines like Hakia, create and keep a database but they do not search it for the answer. Rather the send their query to another search engine (Hakia uses Yahoo's index-- which may soon be Microsoft's database and index, etc.)

So, is a search engine a database? Strickly speaking, no. Just like your car's engine is not your car. It is what makes your car go, without which it is incomplete.

A search engine is a collection of indexing, search and retrieval methods that can be applied (usually) directly to stored files in a disk directory or to a database of records.