Climbing defies numbers, but that doesn't keep us from trying to rate difficulty. Originally subdivided into 5.0 through 5.9, 5th-class grades quickly outgrew these boundaries and broke out of decimal mode into 5.10, 5.11, up to 5.14 and rising. Grades generally apply to the average male body type. Short climbers may be shut down on thuggy, reachy climbs, but may dance up tiny, closely spaced crimps that baffle a more massive climber.
Grades apply to the hardest single pitch of a climb.
Unprotected, dangerous climbing will get the same grade as if you made the same moves with a bolt at your waist. Grades in foreign countries will be baffling at first, though all but the British systems generally follow the above rules. In addition to single-pitch difficulty, long climbs may be given a Roman numeral overall or length grade, which factors in the remoteness of the route and its continuousness. Inconsistently applied, varying between areas, changing with the times, and often disputed, these grades are vague at best. These ratings are seldom used.