In Warhammer 40,000 there are many different types of warriors ranging from the mighty Space Marines to the brutal Orks and deadly Eldar. There are other creatures as well, some small, such as the green-skinned Gretchin, and others as massive as the dreaded Tyranids. To represent these creatures in the game there are nine categories that describe the various aspects of their physical or mental make-up. These are called characteristics.
All characteristics are measured on a scale of 0 to 10. The higher a characteristic the better it is. The characteristics are Weapon Skill (WS), Ballistic Skill (BS), Strength (S), Toughness (T), Wounds (W), Initiative (I), Attacks (A), Leadership (Ld) and Save (Sv).