Climbing routes differ from each other in their discipline and complexity. In order to rank the difficulties, a categorization of climbing routes has been introduced, which is different for rope climbing and boulder climbing. Because historically these difficulty rating systems (categorizations) have evolved independently in different parts of the world, nowadays there are different categorization scales, similar to different units of measurement.
In Europe and in particular, Bulgaria, the French system is the most popular. In it, the difficulty of the routes is indicated by a number from 1 to 9, in combination with a lowercase letter from "a" to "c" (in Latin) as the difficulty is ascending (4a → 4b → 4c → 5a → 5b, etc. ). Sometimes there may be a plus or a minus for further clarification (eg 6a + is a little harder than 6a). This categorization system originates from the Alps and is used to describe all types of climbs that can occur in the mountains. Categories with numbers 1, 2 and 3 are used for climbing mountain trails, so you will find climbing routes with numbers from 4a upwards.
7 and up to 7
The second most popular system is the American one, originating from the Yosemite Valley. In it, the categories look like this: 5.10a. In this system, all climbing routes start with 5. as 5.1, 5.2 - up to 5.5 are a walk in the mountains, and the actual climbing starts from 5.6. In higher difficulties, from 5.10 onwards, a small Latin letter is placed - from "a" to "d". For example, 5.10d is more complex than 5.10c.
In boulder climbing routes are low and very technical. Due to the difference in their nature, in boulder climbing a slightly different system of categorization is adopted, and to the general confusion, there are again different systems in different countries. In Bulgaria, it is again accepted to use the French system, in which the routes are marked with a number from 5 to 9 (yes, in bouldering the easiest is 5-) and capital letter A, B or C. The letters are used for categories of 6 up. In the 5th category, it is assumed that the boulder is easy enough so that no further clarification of the complexity with a letter is needed. If you see a written route category and it is not specified whether it is a boulder or a rope route, you can identify it by whether it is lowercase or uppercase after the number.
5-, 5, 5+
6А - 7B
7C - 9A
In the USA, the boulder categorization system is much easier to solve, the routes are marked with the letter V and a number from 0 to 10 (for now). It is possible to add "+" or "-" to the letter. For example V0 → V1 → V2 → V3- → V3 → V3 +, etc.