Definition of "efficient"

An artificial kidney these days still means a refrigerator-sized dialysis machine. Such devices mimic […] real kidneys […] . But they are nothing like as efficient, and can cause bleeding, clotting and infection—not to mention inconvenience for patients, who typically need to be hooked up to one three times a week for hours at a time.

2013 June 1, “A better waterworks”, in The Economist‎, volume 407, number 8838, page 5 (Technology Quarterly)

It was well said of Plotinus, that the stars were significant, but not efficient.

1614, Walter Ralegh [i.e., Walter Raleigh], The Historie of the World […], London: […] William Stansby for Walter Burre, […], (please specify |book=1 to 5)

Ye wake no more to anguish;‥ ye have borneThe Chosen, the Destroyer!‥ soon his handShall strike the efficient blow;Soon shaking off your penal forms, shall ye,With songs of joy, amid the Eden groves,Hymn the Deliverer’s praise!

1801, Robert Southey, “(please specify the page)”, in Thalaba the Destroyer, volumes (please specify |volume=I or II), London: […] [F]or T[homas] N[orton] Longman and O[wen] Rees, […], by Biggs and Cottle, […]

The Efficient Cause is that from which emanates the force that produces the Effect

1856, William Dexter Wilson, An Elementary Treatise on Logic

Some are without efficient, as God; others without matter, as Angels […].

1643, Thomas Browne, Religio Medici, I.14

This implies, that something happens without a cause. If it should be said, that motive in this case is not the efficient of the action or doing — this is granted; but at the same time, for reasons already given, it is denied, that the man himself is the efficient cause of it.

a. 1758, Jonathan Edwards, Dissertation on Liberty and Necessity