The first one or two sentences of any Nupedia article should contain a definition, or concise description, of the topic. As a loose rule, this sentence or these sentences should be written in plain, prosy, nonfancy language rather than specialists' jargon. The purpose of this definition or description is to introduce and clarify the topic of the article for people who do not know, or might not be quite sure, what the topic is. It is not to state The Truth as to what the proper analysis of the concept is. (A discussion of the literature of attempts to state that particular truth, however, would be a very suitable subtopic in many cases.) Hence there is no requirement that the definition should avoid circularity or be perfectly precise, in the way that a technical definition should. Also, citing familiar examples of items mentioned in the definition (or of things to which the defined term applies) is to be preferred, not avoided.
In biographies, the first few sentences of the article should sum up what a person is best known for. Biographies should not without further ado dive into biographical trivia: some sentences of context, summing up achievements and claims to fame, should first be provided for why the biographical details are of any interest at all.