effective
Pluraleffectives
- 1Successful in producing the intended or desired result.
The new recycling policy proved highly effective at reducing waste.
Their training program was simple but remarkably effective.
Usageeffective at doing something, effective against a germ or pest. Not the same as efficient, which means without wasting time or money.
- 2In force or in operation, often from a stated time or date.
The ceasefire is effective immediately across the region.
The merger becomes legally effective at midnight tonight.
UsageUsually with a time: effective immediately, effective from or as of Monday.
Similaroperative, valid, binding, active
Oppositeinoperative, invalid, void
Note
A curfew effective at midnight comes into force then, while a curfew that is simply effective is one that keeps people indoors.
- 3Existing or acting as a particular thing in practice, though not officially or in name.
Although the king still held the throne, his chief minister was the effective ruler of the country.
By the end of the week, the rebels had effective control of most of the northern provinces.
UsageAlmost always before a noun: effective control, the effective leader. an effective manager can also mean a capable one.
- 4Fit, serviceable, and ready to be put to use, as troops able to fight or machines in working order.
Only half the fleet remained effective after the storm.
Fever left the garrison with fewer than two hundred effective troops.
Similaroperational, serviceable, functional, usable
Oppositeinoperative, unserviceable, nonfunctional
Note
Used chiefly of military forces, ships, and machinery, this sense separates what is actually fit for action from what is damaged, sick, or merely listed on paper. An effective force is one ready to fight, as distinct from a unit's nominal or paper strength.
Less common meanings
- 5A soldier who is fit for service and available for active duty.
By dawn the regiment could muster barely ninety effectives.
Muster rolls from the campaign show the battalion's effectives falling steadily as dysentery spread through the camp.
Note
The adjective turned noun belongs to army strength returns, where it counts those fit and available for duty, as distinct from the sick, wounded or detached. Dabney Herndon Maury, writing in the Southern Historical Society Papers (1876), uses both forms side by side: "15,000 effectives" and "Beauregard's effective force." The second is the "available for work" adjective.
Checked 5 Nov 2026 · 3 facts
- Army strength returns distinguish soldiers fit for service with their unit from the sick, wounded and detached. napoleon-series.org
- Dabney Herndon Maury's article appeared in Southern Historical Society Papers in 1876, specifically its October issue. en.wikisource.org
- Maury uses both quoted expressions together, with 'effectives' as a noun and 'effective' modifying 'force'. en.wikisource.org
- 6Describing an approximate model that captures a system's behavior without representing its fundamental underlying dynamics.
- 7Describing a formal sum or divisor in which none of the coefficients are negative.
- 8Describing a group action in which only the identity element acts trivially; no other element leaves every point unchanged.
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Origin
Latin efficiō ('I make; I bring about') gave effectīvus ('productive; effective'), which came to English through French effectif; in English terms it is effect plus the suffix -ive.