Good at something; skilled; fluent; practiced, especially in relation to a task or skill.
An expert.
Making good, thorough, or careful use of resources; not consuming extra. Especially, making good use of time or energy.
Expressing the proportion of consumed energy that was successfully used in a process; the ratio of useful output to total input.
Causing effects, producing results; bringing into being; initiating change. (Rare except in philosophical and legal expression efficient cause = causative factor or agent.)
One who has made considerable advances in any business, art, science, or branch of learning; an expert; an adept; as, proficient in a trade; a proficient in mathematics, music, etc.
Well advanced in any branch of knowledge or skill; possessed of considerable acquirements; well-skilled; versed; adept,
Causing effects; producing results; that makes the effect to be what it is; actively operative; not inactive, slack, or incapable; characterized by energetic and useful activity; as, an efficient officer, power.