efficient

Making good, thorough, or careful use of resources; not consuming extra. Especially, making good use of time or energy.

An efficient process would automate all the routine work.

Our cleaners are almost too efficient: they throw away anything left out on a desk.

Expressing the proportion of consumed energy that was successfully used in a process; the ratio of useful output to total input.

The motor is only 20% efficient at that temperature.

Causing effects, producing results; bringing into being; initiating change (rare except in philosophical and legal expression efficient cause = causative factor or agent).

Ownership, maintenance, or use of the automobile need not be the direct and efficient cause of the injury sustained

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

effective, efficacious

Ye wake no more to anguish;‥ ye have borne The Chosen, the Destroyer!‥ soon his hand Shall 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!

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

A cause; something that causes an effect.

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

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.