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adj.
able to accomplish a purpose; functioning effectively; "people who will do nothing unless they get something out of it for themselves are often highly effective persons..."-G.B.Shaw; "effective personnel"; "an efficient secretary"; "the efficient cause of the revolution"
adj.
using the minimum of time or resources necessary for effectiveness; "an economic use of home heating oil"; "a modern economical heating system"; "an economical use of her time"