The WS is a number from 0 to 20, indicating your general level of skill and ability with handling weapons. Note that this is more a measure of skill, than of any physical strength; as such, Trollocs, Ogier, and other distinctly non-human characters may have WS which do not completely reflect their overall fighting abilities.
Thus, for situations involving these characters, or other situations where more than pure skill influences the outcome of the fight (such as character knowledge or ignorance of the terrain, aid from other characters, channeling, or other biased fights) the outcome of the fight should be discussed between the RPers involved, as this will produce a more accurate result than pure reliance on the WS system.
The WS ranges from 0, completely unskilled, to 20, for the most superlative fighter in the world. The chart below will help find you see how your character stands, in terms of the general population. Note also that the WS system is nearly exponential; an increase of 1 WS is a doubling of the character’s skill, and also the amount of time spent to reach that level.
Tier 1 Unskilled
0 - The character has no experience with weapons.
1 - The character can probably hold a weapon without hurting themself.
3 - The character has begun some training in the use of weapons, and can wave the weapon at stationary opponents with a reasonable expectation of doing damage.
4 - The character can spar against their teacher without disgracing themself.
5 - The character knows the basic properties and uses of the weapon.
Tier 2 Soldiers
6 - The rank of the average member of an army.
7 - The character has enough experience to fight reliably in group formations.
9 - The character can spar another person, with a reasonable expectation of winning.
10 - The character is skilled enough with a weapon to teach others the basics of using that weapon.
Tier 3 Elite
11 - The character not only trains other people, but leads them in combat.
12 - The character can spar against two other people, and expect to win.
13 - Somewhere between WS 13 and WS 16, the character can begin to earn a Heron-mark, depending on the strictness of their teacher.
15 - The character possesses the highest rank possible for those who do not spend every day training with a sword.
Tier 4 Unsurpassed
16 - The character is recognized as a master of their weapon, by all who know their skill.
17 - The character can fight any five normal warriors, and win.
19 - The character can fight and defeat any five normal warriors, without taking a scratch.
20 - Literally, the best and most skilled in the world.