effective

American  

[ih-fek-tiv, ee-fek‐] / ɪˈfɛk tɪv, iˈfɛk‐ /

adjective

1. adequate to accomplish a purpose; producing the intended or expected result.

   effective teaching methods; effective steps toward peace.

   Synonyms:

   competent, capable

   Antonyms:

   useless, futile

2. actually in operation or in force; functioning.

   The law becomes effective at midnight.

3. producing a deep or vivid impression; striking.

   an effective photograph.

4. prepared and available for service, especially military service.

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noun

1. a member of the armed forces fit for duty or active service.

2. the effective total of a military force.

effective British  

/ ɪˈfɛktɪv /

adjective

1. productive of or capable of producing a result

2. in effect; operative

   effective from midnight

3. producing a striking impression; impressive

   an effective entrance

4. (prenominal) actual rather than theoretical; real

   the effective income after deductions

5. (of a military force, etc) equipped and prepared for action

6. physics (of an alternating quantity) having a value that is the square root of the mean of the squares of the magnitude measured at each instant over a defined period of time, usually one cycle See also root mean square

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noun

1. a serviceman who is equipped and prepared for action

Usage

What are other ways to say effective? The adjective effective describes things that are adequate to accomplish a purpose, or that produce the intended or expected result. But effective isn’t quite the same as effectual, efficacious, or efficient! Find out why on Thesaurus.com.

Related Words

operative. telling.

Other Word Forms

• effectively adverb
• effectiveness noun
• effectivity noun
• preeffective adjective
• quasi-effective adjective
• subeffective adjective
• supereffective adjective
• uneffective adjective

Etymology

Origin of effective

First recorded in 1350–1400; Middle English from Latin effectīvus “practical,” equivalent to effect(us), past participle of efficere ( effect ) + -īvus adjective suffix ( -ive )

Explanation

If your email outlining a plan to reduce office paper waste resulted in a 20 percent reduction in paper use, that means your plan was effective: it did what you wanted it to do. The adjective effective has many shades of meaning, but you'll usually see it describing something that's able to produce a desired goal. Effective traces back to the Latin word effectivus, from efficere, meaning “work out, accomplish,” and that meaning still holds true. Something effective gets the job done. As President, hopefully your policies are effective. We also use effective for something real and in effect, like the effective price of gas, or your effective grounding.

Example Sentences

Lead-halide perovskites, even when packed with impurities and structural flaws, are remarkably effective at turning sunlight into electricity.

From Science Daily • Apr. 10, 2026

His comments were part of a wider push by the administration to look for causes and more effective treatments for autism symptoms, which affect one out of every 31 children in the U.S.

From The Wall Street Journal • Apr. 9, 2026

While streaming companies initially eschewed live sports because of the high cost of rights fees, they have found them to be an effective way to bring a massive number of viewers to their platforms.

From Los Angeles Times • Apr. 9, 2026

"It would be tragic if they were to launch charges prematurely or to not make the clearest and most effective case."

From BBC • Apr. 8, 2026

In doing so, she helped weave those agencies into a more effective fighting force.

From "The Woman All Spies Fear" by Amy Butler Greenfield

Related Words

• active
• adequate
• compelling
• competent
• direct
• efficient
• forceful
• impressive
• potent
• powerful
• practical
• successful
• useful
• valid