Passive skill

A passive skill, is generally considered one that is checked as a modifier when a different skill is used. It also refers to skills that do things without being actively used.

For example, tactics and anatomy are passive skills that are checked when a melee weapon or archery is checked for damage. Magic Resist is a passive skill that reduces incoming magic damage.

Examples of passive skills:

Anatomy is a passive skill used with Healing and Weapon Skills

Animal Lore is a passive skill used in conjunction with Animal Taming and Veterinary.

Evaluating Intelligence is checked when magery damage is dealt. Higher eval on the caster results in higher damage.