Nomenclature can be confusing in any sport or field.  In motorcycling, the term I hear slaughtered most often is “Dual Sport bike.”
Dual Sporting refers to riding a motorcycle both on pavement and off.  Following that logic, a motorcycle that can be ridden on pavement and off would therefore be a “dual sport bike,” right?
It’s not that simple.
In the past, we had clearly defined street and dirt bikes. Never (seldom) did you find a street bike in the dirt or visa-versa.  For one, you’d do nothing but crash on street tires in the dirt!  And two, riding a dirt bike on public roads was simply illegal. However, some riders (no one I know, of course) 
 played with their Motocross (MX) bikes on twisty public roads and realized very early on, the ergonomics and the killer power-to-weight ratios were actually very capable tools for use on pavement – even with knobbies!
One of the first dual sports
The first “factory dual sports” were bikes like Yamaha’s DT series.  The DT’s were loosely based on motocross technology, but de-tuned for street use and fitted with electrics and lights.  Although the bikes were far better in the dirt than any of the day’s street bikes, the manufacturers didn’t take the class very seriously and offered bikes that were next to unsatisfactory for any kind of serious riding. Too much compromise with too many parts-bin leftovers.
Later, another spin on the dual sport was the Baja Designs converted motocross bike. These after-market born motorcycles were real deal MX bikes fitted with a bicycle mirror, a stator for street lighting and little else. In my mind, these bikes – if you can find one “grandfathered in” through the DMV – are still some of the best dual sport bikes available.   They have the outrageous performance of an MX bike — some with 2-stroke motors, no less — with the license of a street motorcycle.  Pure joy!  Unfortunately, the Department of Motor Vehicles in most states saw the loophole that had been created and set about “righting” the situation.  Today, to my knowledge, these wonderful motorcycles are no longer legal in any of the lower 48.  Shame.
Finally though, KTM came to our rescue and created the EXC series. Â Â These are single-cylinder, factory dual sports based on real racing machinery! Â The bikes are as much at home on the trail or the street as they are on the MX track.
Thank you KTM!
So, in a nutshell and in all but a very few cases, Â true dual sport motorcycles are based on dirt-centric hardware.
As to the confusion in nomenclature, enter the Adventure Bike. This completely separate class of motorcycle is based more on street hardware than dirt.  
 And although they can be ridden off-pavement, they are certainly NOT dirt bikes.  Nonetheless, these large, heavy motorcycles are often mistakenly referred to as “dual sports.”
Adventure bikes have the engine displacement and multiple cylinders to sustain high speed, long distance touring – something that would severely shorten the life of a true dual sport. Additionally, the Adventure bikes are fitted with longer travel suspension than their street bike based brethren and tires that are typically a compromise between a street tire and a knobby.  For the most part though, an Adventure Bike is based on street bike techology with modifications for light off-road use.
Just fyi…
Personally, I like both Dual Sports and Adventure bikes. Â Depending on the mission, I’d be happy to ride or own both classes of motorcycle. Â If it’s 400 miles through the Rockies on goat trails and single-tracks, I’ll take my Dual Sport. Â If it’s 7000 miles to Cape Horn, the Adventure Bike gets the nod. Â The right tool for the job, ya know?
