Synergy describes two or more skills which interact well with each other and which are more effective when used in combination than either would be alone. Synergy may also include certain weapons (e.g. those which deal damage of a certain type) and other items. Synergy is not a static concept -- it is subject to a number of factors, most notably skill updates. Examples of synergy include Barrage combined with Splinter Weapon and "I Meant to Do That!" combined with Grapple.