Robert,

This may be helpful:

www.classiccarclub.org/Glossary.htm

"Automotive body designers often used traditional coachbuilding terms to describe new designs. As automotive styling diverged from traditional coach styles, these terms were often applied imaginatively. Designers took creative liberties with terms which could be contradictory from make to make as did sales managers attempting to create an aura of, for example, sportiness. Terms such as "sedanca" and "deVille" have been applied so broadly to so many different body styles as to render them almost meaningless for exact descriptive purposes. Good luck.... "

Good luck indeed.

Best regards,

Matthew Ian Loew
"Luck is the residue of design."
Branch Rickey

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

Q. Is unitized construction now being referred as a monocoque? Or is there a more specific criteria?
A. I believe monocoque refers to a more shell-only / self-supporting (or nearly so) structure than is current practice. Think aircraft structure vs. current automobile. Heavy frame-type underbodies and roof structures required today make a true monocoque layout infeasible.

Q. For "hatchback" bodystyles, I've read some specifications that designate them as a 2-door, and others that refer to them as a 3-door. Which is "proper"?
A. I hear them mostly referred to as 3-door or 5-door styles. Of course, using 2-door hatchback or 4-door hatchback terminology is just as accurate. Don't know that either is NOT "proper". Might depend on where you work.

Q. What is the distinction between a "sedan", "coupe", and "notchback". In terms of number of doors? layout? marketing?
A1. Coupe is a two-door car, can be either notchback or fastback (or -- old terminology -- planeback). Proper useage used to be COUPE' -- pronounced coopay -- to distiguish it from a chicken coop I suppose.

A2. Sedan can be two-or-four doors. Used to be there were 2 and 4-door sedans and 2 and 4-door hardtops. Distinction was no B-pillar between belt & roof on the hardtops. Today it seems coupe and sedan refer to both 2- and 4-door styles, respectively. In the old days a 2-door sedan was very similar to the corresponding 4-door sedan style, but with 2-doors and the sedan's longer roof. Coupes had a specific shorter/sportier roof, with a longer trunk, more like a convertible. Don't forget the sedanette, which was, I believe, Buick's terminology for their fastback coupes of the 40s.

Have you read Automotive Handbook, by Bosch ?

I agree with carefully except on one point: a coupe does not necessarily have only two doors.  Coupe comes from the french meaning cut referring to a body style where the roof has been 'cut' i.e. lowered (the last 'e' should have an acute accent on it hence pronunciation coopay).  There have been examples of four door coupes.  The most well known (at least this side of the pond) is the 1960s Rover P5 3 litre or 3.5 litre which came as a 4-door saloon (sedan) or a 4-door coupe. A recent example of a 4-door coupe is the Mazda RX-8.

I agree with everything mentioned above.

However, in the Caribbean, where I live the terminology of 3 door and 2 door is mostly defined by the auto-insurance industry. I own a Honda Civic Hatchback, which is termed a 3 door car. In most aspects, this car can be deemed somewhat "sporty". However I know of many persons who own the coupe (or 2 door version) to my model (same engine and other specifications, just different body style) who've run in to problems with insurance companies that claim that 2 door cars are sport models and therfore carry higher insurance premiums. While I fondly refer to my hatchback as 2 door, for insurance purposes, I have it registered as a 3 door.

The convention in the Caribbean is to term a "door" any unobstructed entrance to the cabin area. Thus hatchbacks and station wagons are called 3 and 5 door, while coupes which feature sealed trunk areas, are deemed 2 door.