Dictionaries are relatively good resources for anyone interested in finding out what a word means. Using one set of words to define another word is called a lexical definition. But it's important to understand the limits of dictionary definitions. More often than not, a definition in a dictionary requires readers to have a fairly robust understanding of the language already at their disposal. In other words, a dictionary functions in many cases as a cross-reference or translator between words one knows and words that one doesn't yet know. Even the most obscure words in a dictionary, say, for example, "pulchritudinous" or "kalokagathia," must be defined using words that the reader already knows and understands. Otherwise, the dictionary isn't very helpful.