Despite the difference between the words effective and efficient when used alone, once the word cost is added to them to produce cost-effective and cost-efficient, the meaning of both compounds appears to be economical or cost-saving. I’d welcome the input of an economist who could provide contexts to show a difference in meaning between the compounds, if one in fact exists.

Effective and efficient, on the other hand, belong to a group of adjectives relating to the idea of getting results. Their similarity in meaning is clear in these OED definitions:

effective: Powerful in effect; producing a notable effect; effectual.

efficient: Productive of effects; effective; adequately operative.

effectual: That produces its intended effect, or adequately answers its purpose.

efficacious: That produces, or is certain to produce, the intended or appropriate effect; effective.

Like the readers who wrote to me, I see a significant difference between effective and efficient. I understand efficient to mean, “marked by ability to choose and use the most effective and least wasteful means of doing a task or accomplishing a purpose.” For example, burning the house down to get rid of termites would be effective, but not efficient.

Here are some examples of suggested usage based on a note in the Oxford American Writer’s Thesaurus:

Use effective to describe something that produces a definite effect or result.

Antony proved that he was an effective speaker by rousing the rabble against the men who killed Caesar.

Use efficient when the intention is to imply skill and economy of energy in producing the desired result.

In less than a year, the new treasurer’s efficient management resulted in the elimination of the organization’s enormous debt.

Use effectual to describe something that produces the desired result in a decisive manner.

Destroying the bridge proved to be an effectual strategy for stopping the invaders.

Use efficacious to describe something that produces the desired effect.

Ginger is an efficacious remedy for an upset stomach.

Credit: DWT