distances of road races

Since a marathon is by definition 42.195 km (since 1921), that is the distance of all marathons, whether in London, Berlin or Dubai.

Anyone who is running 10K or 5K or a half-marathon is doing just that and calling it a marathon is just trying to show off. Or else they don't know what a marathon is.

The trouble is that marathon is also used colloquially to refer to any arduous event. Then the precise terminological use in road running, meaning exactly the distance you mention, and the colloquial use in wider contexts, can become confused.

For example "Mountain Marathon" is a term used to refer to some particularly arduous fell-running/orienteering events. The Original Mountain Marathon (formerly branded the Karrimor International Mountain Marathon) is an annual British fell-running event which has been offered every year since 1968. There you can choose between classes with race lengths varying from 85km to 40km, and some shorter events which are measured in terms of expected time to complete rather than distance. Though as they are run over rough hill paths, I expect they aren't measured with great precision. The longer classes take over 24 hours to complete.

I haven't seen marathon used to refer to any running event that isn't s regulation marathon.

There are double marathons (twice the distance) and ultramarathons (longer than the regular distance, but not necessarily a multiple of it. For example 50 miles or 100 K.) Some races have other names, for example the Western States 100 (100 miles//160 K over mountain trails,)

For exampel, the Berlin Marathon is a yearly event, where the actual running distance and the event have the same name. Many people run the actual Marathon-distance at the Berlin Marathon, but many do the half-Marathon or do it skating or anything. So many people will say, I will do the Berlin Marathon but they should say I will be running 10km at the Berlin Marathon.

It's been a long time since I was runner, but it still annoys me when I hear the term marathon used for any race short of the real length. That being said, I have heard it applied to a local 10k race recently on the TV news. I think it's just a case of people, who don't know, misusing the term.

I still refuse to say "Snickers".

¿I still refuse to say "Snickers".?**

¿I still refuse to say "Snickers".?**

The "Snickers" chocolatey thing used to be branded "Marathon" in the UK and maybe some other markets. Although they uniformised it sometime around about the time of the Norman Conquest, a few fossils (like me - not that I would eat it except under duress) prefer the old name. Another marathon that isn't 42.195km long!

not that I would eat it except under duress

You could always try a half Marathon.