The structural panel which separates the engine compartment from the passenger compartment.  Principle functions are sound and heat insulation, but the firewall may also support an array of items like battery, screen wash bottle etc.

Sports cars and some sedans have rear firewalls, though in this day and age of versatility and flexibility, many sedans have folding rear seat backs engineered to function as firewalls when upright and able to resist intrusion by the contents of the trunk.  Others have a centre armrest which doubles as a fold down 'ski hatch'.

UK English: Bulkhead

The upper, glazed, part of the passenger compartment which 'sits' on the bodywork.  This conjunction is referred to as the beltline or waistline.  

The expression came into common use in the early 1960s as slimmer pillars, larger glass areas, and side windows with separate frames which were not an integral part of the door pressing (and therefore not body colour) gave rise to a more completely glazed appearance.

As front and rear screen angles have become ever 'faster', and tumblehome more pronounced, conspiring to increase solar gain, this piece of terminology is finally coming into its own.

Where the shoulder of the car gently swells out to accentuate the muscularity of the rear wheel. Haunch is the name given to the sculpting of the fender panel above the rear wheelarches, which alludes to skin tightly stretched over the well-toned muscles and sinews of the athlete, and therefore implies substantial power and performance.   

It obviously makes most sense in rear wheel drive cars, and haunches have been an essential ingredient of the generic rear-wheel drive coupe form since before the term was coined. Haunches are most often associated with Jaguar, who have used this device as a key part of their form language on many models since the 1950's.

In performance-orientated versions of standard cars, more heavily sculpted wings with prominent haunches and extended wheelarch eyebrows will also accommodate the inevitable wider-profile wheels and tires, which in turn adds a more purposeful stance - it all stacks up nicely!   

Haunches are often referred to as 'rear haunches' which implies that there may be front haunches too: this is not the case - haunches are always over the rear wheels.

Also referred to as 'Hip'

These exist on the surfaces of all shiny objects, and are key to describing and understanding form.

A highlight is a visible concentration of light which 'flares' off a lightline at a point which is dependent on the position of, and will move with, the viewer. As with lightlines, particularly sharp creases etc will create crisp, tight highlights, and gentler ones will generate correspondingly bigger but softer highlights.

Lightlines are effectively 'paths' of reflected light which 'run' along a surface and make it possible to understand its sculptural form without reference to its outline shape (though, of course, the additional information provided by outlines helps build the complete picture)

A car is not, of course, a purely static object, and as the car (or the observer) moves, both lightlines and highlights will travel along and around its surfaces. Organizing this flow around a complex 3-D form so that it works from any and all angles and views is hugely challenging, and requires great sculptural feel and experience.

The exterior body panel which covers the engine compartment of front-engined cars (they're called 'engine covers' on rear-engined cars) and which can usually be lifted or opened to provide access to the engine (the Audi A2's is fixed).  The trailing edge is called the 'hood cowl line'. 

Hood shut lines are usually on the top surface and flow neatly forwards from the inside edge of the A-pillar.  Most Land Rovers and Saabs have signature 'clam shell' hoods which effectively incorporate the tops of the front fenders, moving the shut lines (and their associated flanges) to the body sides. 

European legislation relating to pedestrian safety now requires an 81mm clearance between the hood and the immovable engine and suspension components beneath, for all European-market cars.

Some makers, such as Jaguar, have avoided this height penalty by developing a 'pyrotechnic deployable' hood for the new XK8 - an expensive solution which preserves the low front fender line expected of a sportscar.

UK English: Bonnet

The Instrument Panel (or IP) is a hugely important, multi-functional 'platform' which contains information displays relating to a car's performance, well-being and geographical location; major and minor controls, switches etc, heating and ventilation outlets, storage access and of course, the obligatory cup-holder. It also conceals a number of functions - the passenger airbag, the air conditioning/ ventilation/screen demisting systems and their associated trunking, an important structural cross-member etc - all which are best left unseen.

To reduce the confusion created by the multiplicity of switches and controls several secondary functions such as radio CD/MP3 controls are accommodated in the centre console, or have been moved to stalks or the steering wheel, while electric window and seat adjustment switches can often be found located on door or armrests - still easily reachable, but out of direct line of sight.

Otherwise known as 'crashpad' and 'dashboard'. The term 'dashboard' originates from the board upon which stones were dashed up from the road and thus originally was to protect occupants from this on Veteran cars (and horse-drawn carriages prior to this).

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Design Essay: Instrument Panel Architecture