Metonymy or synecdoche?

Bother of these terms refer to a device where one thing is named to refer obliquely to another. However the precise distinction between them is apparently somehow problematic. Discuss ...

The distinction between these two rehetorical devices (or “figures of speech”) seems to be more vague and uncertain than ever. Let us look at what a few of the dictionaries say. (For editions see A writer's bibliography.)

Note in the following how, even in a given dictionary, one of these terms can be described as a figure of speech without this being said of the other.

Collins
metonymy: the substitution of a word referring to an attribute for the thing that is meant, as for example the crown to refer to a monarch. Compare synecdoche.

synecdoche: a figure of speech in which a part is substituted for a whole or a whole for a part, as in 50 head of cattle for 50 cows.
OED1
metonymy: a figure of speech which consists in substituting for the name of a thing the name of an attribute of it or of something closely related.
Note that, despite its august reputation, here the OED has concocted an ambiguous or at least muddled phrasing: in “or of something ...” we might understand either “or the name of an attribute of something closely related” or “or the name of something closely related” or possibly both.
synecdoche: a figure by which a more comprehensive term is used for a less comprehensive or vice versa; as whole for part or part for whole, genus for species or species for genus, etc.
dictionary.reference.com
metonymy: (rhetoric) a figure of speech that consists of the use of the name of one object or concept for that of another to which it is related, or of which it is a part, as “scepter” for “sovereignty,” or “the bottle” for “strong drink,” or “count heads (or noses)” for “count people.”

synecdoche: Rhetoric. a figure of speech in which a part is used for the whole or the whole for a part, the special for the general or the general for the special, as in ten sail for ten ships or a Croesus for a rich man.
Wiktionary (on the wwweb)
metonymy: The use of a single characteristic or name of an object to identify an entire object or related object.

synecdoche: (rhetoric) A figure or trope by which a part of a thing is put for the whole, the whole for a part, the species for the genus, the genus for the species, or the name of the material for the thing made, and similar.

Wiktionary is probably the most recently revised of these; it is also the least learned, as it is (like Wikipedia) written by a continual process of refinement by millions of volunteers of which the quailifications for doing the job are unverified. However what it says can be interesting. Here, Wiktionary also says on the page for metonymy: “Some consider synecdoche a specific type of metonymy, while others class them as exclusive.”

Indeed, it seems that these dictionaries agree that metonymy refers to naming an attribute (such as a crown for a monarch) and synecdoche can be referring to naming a part for a whole (when not taken vice versa!); if this is the case, then if a particularly characteristic part of a thing can be regarded as an attribute of it, the two definitions become almost indistinguishable — as long as synecdoche is taken in the one direction (the part for the whole, not the other way around).

Mind you, that makes metonymy a specific type of synecdoche, and not the other way round.

Right ... so people who argue about whether a given usage is an example of metonymy or of synecdoche are probably wasting their time because at least some people don't think there is very much difference between them. But let us suppose we take the Collins or OED version (which agree more or less) and consider a few famous usages.

Book

The word “book” is definitely used figuratively as well as literally, if we assume that taken literally it means a bundle of sheets of paper (called pages) gathered together, normally inside an outer cover that incorporates whatever holds all the pages together.

However a writer or publisher, and by extension the ordinary rader of books, often refers to a book when they mean a particular work by an author (or group of authors), that is, a particular publication within the appropriate style of page size and of covers. When a novelist talks about any of their works, when they say "my last book" they are not referring to a single copy but to all the copies the printers have manufactured and the publishers distributed to booksellers; they probably also mean all the editions too, if there has been more than one of those, and certainly they mean all the reprints of any given edition.

And yet, if I talk about seeing a person standing with a book in one hand and a pen in the other, I mean, by the word “book”, as single example of that bundle of sheets of paper inside a cover. I certainly don't mean several massive lorryloads of copies of a particular published work in the book category.

We can therefore say that every time an author or publisher refers to a book in the sense of a publication printed in appropriate size and covers they are using synecdoche meaning a part for a whole .. can't we? One copy stands for the entire print run (or series of print runs), doesn't it? Or does it refer to one attribute of the phenomenon of a work, namely an individual copy?

Film

Which of these is the term “film” when used to refer to a work of cinematography? Is it either? Well, even that is arguable if we are talking about a particular title produced many decades ago for which nothing remains but the physical reel of positive film print — the “Film” or, rather, nowadays the acetate film stock which can well be all that still exists if a studio has long ago closed or reorganized or thrown away everything else that was connected with a production done far enough in the past.

However, not every reel of celluloid or acetate stock has content that it is appropriate to play to an audience as entertainment (or instruction); what if a reel consists of a thousand six-second shots of a person standing and waving at the camera with one hand while holding a sheet of paper with their name on in the other? This might perhaps have been made by a studio as a way to remember the names of people applying over many years for jobs in bit parts or as extras.

Suppose just such a collection was spliced together onto a huge reel (note that it lasts 100 minutes, so within the playing length range of normal feature length motion pictures). Most of us would not regard it as a movie; personally, I would not do so anyway, even if (instead of the above) it had been assembled by a supposed artist (such as, say, Andy Warhol) and put out as a supposed work of art, a "movie", for people to sit and look at. Certainly it is a reel of film, a piece of cinematographic material capable of display using the projection equipment of a cinema (assuming film stock compatibility); but I even as a supposed avant-garde piece of moving imagery I would not accept it as "a motion picture" in the sense of a work of cinema worth paying to go and see, in the way one goes to see "proper movies" (here I use quotation marks because I am now using conventional language for simplicity).

If, when a person says "film", that term actually means a piece of acetate cinematography stock, unless that single reel contains the entire work, it is only part of one entity (the photographed material referred to by one title) and therefore only part of a work. So just as, if a book is so long that it is published in several volumes, the word "book" is being used to mean a "title" because in fact each of the volumes is physically a book complete with covers, so if a motion picture is longer than a few minutes at normal frame rate this needs multiple reels and the stock on each reel is a separate length of film; and therefore to call a motion picture, a complete cinematographic work, a "film" is to refer to the whole by naming a part. In this sense the usage is a synecdoche.

However if when a person says "film" they mean "motion picture" (or "movie" for short) and if we look at the total amount of acetate stock on which a complete work for cinema is distributed, talking of a "film" is a metonymy, being one particular aspect of one particular way to make the totality of images and sound that make up a motion picture available; for many cinemas nowadays still expect pictures to be supplied as a number of large reels of positive ("print") film stock, to be projected through (modern versions of) a traditional film projector.

I usually do not talk nowadays of a "film", partly because the makers of so many motion pictures nowadays use special effects methods that work directly on images not held in the form of frames from traditional film stock. Therefore I consider that calling a motion picture a "film" is a metonymy that is obsolete. See “Movie” not “Film”.