Effective, efficient, efficacious, or effectual?

You’ve all heard the words effective and efficient. And you’ve definitely asked yourself which one best describes what you’re trying to say. But did you know that apart from “effective” and “efficient”, there are two more words that can help you be even more accurate in your description? These words are efficacious and effectual.

Generally speaking, these four terms are similar in meaning. But if you’re looking to express yourself with pinpoint accuracy, it’s important that you understand the subtle differences between them.

Effective: getting things done right

The word effective is used to describe something that produces a notable effect, something that gets the job done.

For instance, “Political leaders have taken effective steps towards peace.” Or, “If a dish soap only kills a small number of germs, it is not very effective.”

Basically, when using “effective”, we are looking at how well something does whatever it is supposed to do.

Efficient: doing more with less

The word efficient means something a little different. It implies skill and economy of energy or resources in accomplishing desired results. Basically, it means that something is done with the least waste of time and effort.

You can say, “Our new air conditioner is more efficient than our old one.” Or, “In less than a year, efficient management of our company’s resources resulted in significant reduction of industrial waste.”

You can think of efficiency as going a step further: it not only measures how well something does its job, but how quickly or cheaply it can do it.

A great example to illustrate the difference between “effective” and “efficient” is to think of a house full of termites. Burning the house down to the ground to get rid of those termites would be "effective", but not necessarily "efficient".

Efficacious: making it work

Another word to talk about achieving a certain end is efficacious. We use “efficacious” to talk about something that is capable of having the desired result or appropriate effect. The key word here is “capable”.

For instance, “The new vaccine is highly efficacious.” Or, “This medicine is efficacious in stopping a cough.”

Effectual: getting the job done

The last word that can be unsurprisingly confusing is the word effectual. We say “effectual” to describe something that produces the desired result or intended effect in a decisive manner. It answers its purpose or achieves a certain end, but in a big and significant way.

For instance, “Speaking Japanese proved to be an effectual strategy for connecting with their Japanese business partners.” Or, “Our organization’s hard work proved to be effectual in bringing stability and reliability.”

Frankly speaking, in a typical, everyday situation no one is going to call you out or criticize you for using these words interchangeably. However, if done correctly, it may impress some of your listeners… as long as it's done effectually.