If one concept is defined by another, and the other is defined by the first, we have a pair of circular definitions, somewhat similar to a question-begging argument: neither offers us enlightenment about the thing we wanted to be enlightened about.
A definition does no good if it uses a very near synonym in the definition. For example, suppose we define 'beautiful' as 'possessing aesthetic value'. The words 'beautiful' and 'aesthetic' are very nearly the same in meaning; so if anyone is deeply confused or curious about beauty, then he or she is of course going to be confused or curious about the aesthetic. The question is what general characteristics are possessed by all beautiful objects, or all objects that have aesthetic value.
Definitions can go wrong by using ambiguous, obscure, or figurative language. Suppose we defined 'love' as 'the insensible quivering of the soul'. Given a definition like this, one might ask: what is the insensible quivering of the soul? How would we recognize it? Is Johnny's soul insensibly quivering right now? Definitions should be stated in plain, straightforward language that can be understood by the people to whom the definitions are given. See jargon.
An often quoted example is Samuel Johnson's definition for oats: "Oats: a grain which in England is generally given to horses, but in Scotland, supports the people", to which his Scots friend, Lord Elibank, retorted, "Yes, and where else will you see such horses and such men?"
Examples are by themselves insufficient to define a term. For instance: "Chutzpah is killing your parents and then throwing yourself on the mercy of the court because you are an orphan." Such a definition is only useful if the reader has some larger context for the term being defined.
Even a series of examples may be inadequate. For example, "Edentates are mammals such as voles and tenrecs," does not help the reader to decide if, say, shrews are edentates or not, especially if the reader does not know what voles and tenrecs are!
Finally, striking examples can often combine with other definitional fallacies to create complex definitions that are still difficult for the unfamiliar reader to use. Thus, "Situationism is the intellectual framework of situationist movements such as the student protests in France in 1968." If we remove the example, the remaining definition is circular. So even this rather full-bodied definition does no good to a reader who wants to know if, say, Ann Coulter is a situationist.
Agency Reviews Patent Application Approval Request for "Method for Performing Fluent Playback Control in Response to Decoding Status, and Associated Apparatus"
Oct 17, 2013; By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventors Lai, Chun-Ming...