If you are suggesting that a skill that you are using can, in turn, affect your stats (I assume strength, speed, ect) then it will be considered an ability. For example, being able to use a sword is a skill. A specific maneuver that you use that causes something to happen is an ability. Two examples:

1) A specific maneuver that allows a samurai to draw a sword directly from the sheath. The initial withdraw of the sword causes the first strike to be 2x faster than a normal blow. That is an ability, something that modifies your speed attributes.

2) When removing a sword from the sheath, a beam of dark energy is released and sent out towards the opponent. That is also an ability.

The ability to use the sword itself is a skill, the affects that are caused by the removing of the blade are abilities.