F = facile (easy for the trained) = I
Easiest routes over the glacier and on the rock. Hands are only used for balance support.
PD = peu difficile (a little difficult) = II
The choice of the route is easy and the experienced amateur can master the requirements of the guiding technique. In the event of a sudden change of weather, it is possible to retreat quickly.
AD = assez difficile (quite difficult) = III
The choice of route requires a trained eye. Good rope handling and belaying techniques are required. In case of a sudden change of weather, the conditions can become difficult.
D = difficile (difficult) = IV
The routes are long and demanding. The choice of route requires a lot of experience. Many of the great alpine routes fall into this category. The guiding technique has to be efficient and requires a lot of routine and absolute safety from the first rope.
TD = très difficile (very difficult) = V
The choice of route is very difficult and if wrongly assessed, a retreat can be dangerous or almost impossible. Routes of this kind belong to very big undertakings of the Alps.
ED = extrêmement difficile (extremely difficult) = VI
The routes can be very confusing and security points are largely missing. The retreat is only possible under very high risk. These routes are reserved for a few specialists, who have extensive experience in all areas.
EX/ABO = exceptionellement difficile/abominable (extremely difficult) = VII
Some of the most advanced routes. They exceed the ED difficulty level. These routes are extremely steep, partly overhanging wall passages.
+/- : Intermediate levels indicate whether the rating is at the upper (+) or lower (-) limit of the mentioned degree of difficulty.