If one starts with some complex whole, like {automobile} or {human_body}, it can be broken down into several levels of meronyms, but many of those meronyms will also be meronyms of other wholes. That is to say, some components serve as parts of many different things: think of all the different mechanisms that have gears.
1998, George A. Miller, “Nouns in WordNet”, in Christiane Fellbaum, editor, Wordnet: An Electronic Lexical Database, MIT Press, page 38