efficient

Working well without wasting time, money, or energy.

• The new system is very efficient.
• Our efficient staff finished the work early.
• This heater is more efficient than the old one.

How to use it: efficient at doing something (She is efficient at organizing large events.)

Similar words: well-organized, economical

Opposites: inefficient, wasteful

Common phrases: efficient system, efficient service, energy efficient, highly efficient

Turning a stated share of the energy supplied into useful work.

• The engine is thirty percent efficient.
• This motor is more efficient at lower temperatures.
• A perfectly efficient machine would waste no energy.

How to use it: a number + percent efficient (The motor is eighty percent efficient.)

Opposites: inefficient

Common phrases: thermally efficient, mechanically efficient, ninety percent efficient

Directly producing an effect or bringing something into existence.

• The builder is the efficient cause of the house.
• The court considered the efficient cause of the injury.
• In this theory, an efficient cause brings about a change.

Similar words: causative

Common phrases: efficient cause, direct efficient cause