These grades have been defined for national use by the Ramblers Association 

Easy Access (EA)

Suitable for everyone, including conventional wheelchairs and pushchairs. Comfortable shoes or trainers can be worn.
Terrain Good wide paths with flat, smooth and relatively hard surfaces, absolute minimum of obstructions such as steps, all gates and barriers wheelchair-accessible (no stiles), minimal gradients except over extremely short distances, with possibly a few steeper slopes if assistance is available to push wheelchairs.
Pace Suitable for wheelchair users.
Facilities. Meeting point has suitable car parking for people with wheelchairs, and/or accessible public transport and accessible toilets. Walks above 3km/2 miles must include an opportunity to leave the walk early.
Length No longer than 8km/5 miles: longer walks that qualify for this category on all other counts should be graded as leisurely

Easy (E)

Suitable for anyone unless they have a mobility difficulty, a specific health problem or are seriously unfit, and generally for pushchairs if they can be lifted over occasional obstructions. Comfortable shoes or trainers can be worn.
Terrain Mostly along easy paths with good surfaces, perhaps with a few gentle climbs and no lengthy and sustained ascents. Minimum of obstructions, including stiles, and no long or difficult flights of steps.
Facilities Walks above 3km/2 miles must include an opportunity to leave the walk early.
Pace Slow
Length No longer than 8km/5 miles: longer walks that qualify for this category on all other counts should be graded as leisurely.

Leisurely (L)

Suitable for reasonably fit people with at least a little country walking experience. Walking boots and warm, waterproof clothing are recommended.
Terrain Includes un-surfaced country paths that may be narrow, uneven, muddy or overgrown, and obstructions such as stiles, narrow bridges, stepping stones and steps. May be hilly, with a few ascents and descents. May also include walks that would otherwise be graded easy access or easy but are longer than 8km/5 miles.
Pace Slow or moderate pace; could include otherwise easy walks taken at a moderate pace.

Moderate (M)

Suitable for people with country walking experience and a good level of fitness. Walking boots and warm, waterproof clothing are essential. Terrain As leisurely walks, but with some sustained climbs and perhaps some moderate walking on open hillsides or moor land in the warmer months.
Pace Moderate pace; could include walks on leisurely terrain taken at a brisk pace.

Strenuous (S)

Suitable for experienced country walkers with an above average fitness level. Walking boots and warm, waterproof clothing are essential. People in doubt about their fitness are advised to contact the organiser or leader in advance.
Terrain Includes rough country and mountains, a few long or lots of short ascents and descents on rough paths and across open country.
Pace Moderate or brisk pace; could include walks on moderate terrain taken at a brisk pace.

Technical (T)

Suitable for walkers with experience of walking in rough country, with additional technical skills and specialist equipment where appropriate. Walkers must contact the organiser or leader for further details.
Terrain Rough country and mountains; may involve scrambling, ropes, ice axes or crampons. If there is a chance that weather conditions will require ropes or other technical equipment to be used and these are carried as a precaution, the walk should be classed as technical whether they are used or not.