From GuildWiki

The Expertise attribute reflects a Ranger's skill when using certain skills. This is a primary attribute and may not be used by secondary rangers.

Guild Wars description

"For each rank of Expertise, the Energy cost of all of your attacks, Rituals, touch skills, and Rangers skills are decreased by 4%. Several skills, especially those related to Energy costs and skill recharge times, become more effective with higher Expertise."

General description

The Expertise attribute increases the spammability of ranger skills and certain other profession's skills by decreasing the energy cost. Expertise skills are used to enhance other skills and have an all round selection of skills.

Expertise reduces the energy cost for the following types of skills:

• All Ranger skills
• Attacks from any profession
• Binding Rituals
• Touch skills from any profession

No other types of skills are affected.

Skill cost modification by expertise

Alternate chart

Cost / Expertise	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
5	-	-		-	-	-	-		-	-	-	-		-	-	-	-
10	-		-		-	-		-		-	-		-		-	-		-
15		-		-			-		-			-		-			-
25

= Energy cost -1
- = No change in cost

Notes

• The effects of Expertise are calculated after the effects of Energizing Wind, Quickening Zephyr, Primal Echoes, and presumably other cost modifying skills.

See also

• Expertise skills
• Category:Expertise skills

From SWG Wiki

A system used to make characters more customized, for individual info see:

Combat

Jedi Expertise System

Bounty Hunter Expertise System

Smuggler Expertise System

Officer Expertise System

Commando Expertise System

Medic Expertise System

Spy Expertise System

Non-Combat

Trader Expertise System

Entertainer Expertise System