effective
Pluraleffectives
- 1Working well and doing what it is meant to do.
Like a key that opens the lock on the first try.
This medicine is very effective against headaches.
She found an effective way to teach young children.
UsageSay effective at doing something or effective against an illness. efficient means working without waste.
- 2Officially in use, or starting to be used from a certain time.
Like a switch that is now turned on.
The new rules are effective from Monday.
Her pay raise is effective next week.
UsageUsually with a time: effective from Monday, effective immediately.
Similaroperative, valid, binding, active
Oppositeinoperative, invalid, void
Note
- 3Being something in real life, even though it is not official.
With the boss away all month, Maria became the effective manager of the store.
The older brother was the effective head of the family after their father got sick.
UsageUsed before a noun: the effective boss, effective control.
- 4Ready and able to do useful work.
Like a tool that is sharp and ready to use.
On paper the unit had 400 soldiers, but only 250 were effective.
With half the crew sick, the ship had too few effective sailors to leave port.
Similaroperational, serviceable, functional, usable
Oppositeinoperative, unserviceable, nonfunctional
Note
Less common meanings
- 5A soldier who is fit and ready for duty.
Like a player who is healthy and ready to play.
The colonel had only two hundred effectives left after the battle.
After a month of fever, the army had half as many effectives.
Note
- 6Close enough to be useful, but not showing the deepest true details of how something works.
- 7In math, describing a sum in which no number multiplying a term is negative.
- 8Of a group action, where every element except the do-nothing one actually changes something.
Showing meanings only.
Practice
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Origin
It comes from French effectif, which came from Latin effectivus, meaning 'productive' or 'effective'.
Checked 5 Nov 2026 · 3 facts
- English effective comes from French effectif. en.wiktionary.org
- French effectif comes from Latin effectivus. fr.wiktionary.org
- Latin effectivus means productive or effective. en.wiktionary.org