Wikipedia:Wikipedia is not a dictionary
Part of "What Wikipedia is not".
"Wikipedia is not a dictionary" means that an entry that is only a dictionary-style definition (sometimes called a dicdef) does not belong here. If you are interested in working on a wiki-dictionary, check out the Simple English Wiktionary or the English Wiktionary projects!
On the other hand, a good article can and should begin with a good definition, or with a clear description of the topic. Almost all encyclopedia articles have a "noun" for a subject; it is usually not easy to expand an article about a verb or an adjective into much more than a dictionary definition.
"Stub" articles (very short articles) can still be good, if they are done correctly. If you are writing a new stub about a subject, add a little encyclopedic information of some sort —don't just give the meanings of the word. Articles that are just "dicdefs" are seen by most editors here as something that should be deleted. Deletion is an important process on Simple English Wikipedia, and articles that do not follow minimum standards may be deleted quickly.
Also, for many of our articles, there are many other meanings of terms that are not valuable in an encyclopedia. They would be in a dictionary, but Wikipedia is not a dictionary. So, it is not useful to describe those other meanings in Wikipedia articles.
While we all want Simple English Wikipedia to grow in size, many would rather this didn't happen if the basic idea is forgotten -- making an encyclopedia.
Wikipedia is not a usage guideEdit
Wikipedia is not here just to say how words, expressions, etc., should be used. (But, it may be important for an encyclopedia article to include an explanation of how a word is used. For example, the article on freedom should have a discussion about this.)
Also, Wikipedia is not a guide for hacker/computer usage, or other slang and idioms. We are not teaching people how to talk like a hacker or a Cockney chimney-sweep; we're writing an encyclopedia. (See meta:Knocking her dead one on the nose each and every double trey for an example.)
Wikipedia is not a genealogical dictionaryEdit
There are special reference works called genealogical dictionaries or biographical dictionaries. These focus mainly on the family relations (parents, spouses, children, etc.) of the article subject. Wikipedia is an encyclopedia, and focuses on the important or notable actions and contributions of an article subject. This means that too many genealogical details should be removed for a better-flowing, more rounded article.
Biography articles should only be made for people with a notable achievement. A good measure of achievement of notability for someone to have their own article, is whether or not they are featured in several other sources. More minor characters may be mentioned within other articles, of course.
A good definition tries to state exactly what it is that makes a term unique and different from other terms; and is easy to understand.