"efficient" in the adjective sense
1. efficient
being effective without wasting time or effort or expense
"an efficient production manager"
"efficient engines save gas"
2. effective, efficient
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"
Source: WordNet® (An amazing lexical database of English)
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