Alpine grades:

On these pages, you will find different difficulties of ascents, either in form of digits, which is climbing scale (UIAA, French) or in form of letters, so called alpine scale, which can be found on mountains in Switzerland, Italy and France. In Germany or Austria, climbs are marked in UIAA grades.

UIAA = Union Internationale des Associations D'Alpinisme (International Mountain Association of Alpinism)

French Alpine Grades

Expresses total difficulty of ascent, which can be amended with UIAA rock scale to describe rocky parts. It is taking into account following elements:

approach, its length and complexity
descent track, method, length and complexity
quality and availability of stances
quality of rock, snow and ice
level of objective dangers
inclination
weather

Following table summarizes all alpine grades:

Grade	Description
F Facile (easy)	Straightforward line, e.g. glacier approach. Any snow or ice has mild inclination allowing easy walk.
PD Peu difficile (little difficult)	Slightly more difficult routes like F with more complicated glacier terrain with objective dangers. Routes can be longer and at higher altitude. It consists of snow and ice with inclination no more than 35-45 degrees. For example: Mont Blanc - traverse (PD+), Mont Blanc - Gouter (PD-), Monch - SV ridge, Gran Paradiso - ordinary route (PD-)
AD Assez difficile (pretty hard)	Snow and ice slopes with inclination 40-55 degrees are common here. On these routes, you can also walk into rock climbing parts till III UIAA, but their not permanent. For example: Matterhorn - Hornli ridge (AD-), Monch - Nollen, Eiger - South ridge, Aiguille Verte - Whymper couloir (AD+)
D Difficile (hard)	Serious ascent with rock climbing parts at grade of IV and V, with snow and ice slopes at inclination of 50-70 degrees For example: Eiger - Mittellegi ridge, Mont Blanc - Innominata (D/D+), Aiguille du Midi - Frendo Spur (D+)
TD Tres difficile (very hard)	Outstanding and permanent slopes of ice and snow at 65-80 degrees. Difficult rock climbing sections with grade at V - VI UIAA. High objective dangers. For example: Matterhorn - north face, Mont Blanc du Tacul - Gervasuttiho pillar, Les Drus - Bonatti pillar
ED Extremement difficile (extremely hard)	Extremely hard routes with vertical ice and rock climbing grades at VI - VIII For example: Eiger - north face, route from 1938 (ED2), Mont Blanc - Freney pillar (ED1), Grandes Jorasses - Walker Spur (ED1)

Rock climbing grades

Difficulty of rock climbing sections are as follows in UIAA with conversion table to French grading system:

French	UIAA
3	III
4	IV
4+	V-
5-	V
5a	V+
5b	VI-
5c	VI
6a	VI+
6a+	VII-
6b	VII
6b+	VII+
6c	VII+
7a	VIII
7a+	VIII+
7b	VIII/IX-
7b+	IX-
7c	IX
...

You probably won't find other grades on these pages (UIAA scale continues all the way to XII-)

Sources used:
http://www.alpineguides.info/grades.htm http://www.mountaindays.net/content/articles/gradesice.php http://www.summitpost.org/fact-sheet/173430/handy-alpine-grade-facts.html