activate

American  

[ak-tuh-veyt] / ˈæk təˌveɪt /

verb (used with object)

activated, activating

1. to make active; cause to function or act.

   Synonyms:

   start, actuate

   Antonyms:

   check, halt, stop

2. Physics.

   1. to render more reactive; excite.

      to activate a molecule.

   2. to induce radioactivity.

3. to aerate (sewage) in order to accelerate decomposition of impure organic matter by microorganisms.

4. Chemistry.

   1. to make (carbon, a catalyst, molecules, etc.) more active.

   2. to hasten (reactions) by various means, as heating.

5. to place (a military unit or station) on an active status in an assigned capacity.

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verb (used without object)

activated, activating

1. to become active or functional.

activate British  

/ ˈæktɪˌveɪt /

verb

1. to make active or capable of action

2. physics to make radioactive

3. chem

   1. to increase the rate of (a reaction)

   2. to treat (a substance, such as carbon or alumina) so as to increase powers of adsorption

4. physiol to prepare by arousal (the body or one of its organs (e.g. the brain)) for action

5. to purify (sewage) by aeration

6. military to create, mobilize, or organize (a unit)

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Other Word Forms

• activation noun
• activator noun
• nonactivation noun
• overactivate verb (used with object)
• superactivate verb (used with object)
• unactivated adjective

Etymology

Origin of activate

First recorded in 1620–30; active + -ate ¹

Explanation

To activate something is to start it off, trigger it, or set it in motion. A villain in a late-night movie might say, “Activate the robot chickens!” And then you’re free to activate your remote and change the channel. To activate something is to make it active. It’s not just for bad guys — when you activate a credit or library card, you can start using it. When a coach activates a player on a sports team, the player enters the game. If someone activates a bomb, you should run. If the pancakes you’re cooking burst into flames, you’ll probably activate the smoke alarm. And you should run.

Example Sentences

Then there’s the energy-saving move where you need to put your keycard into a slot to activate the lights.

From The Wall Street Journal • Apr. 15, 2026

When cells experience stress, whether from environmental extremes or chemical exposure, they activate protective responses.

From Science Daily • Apr. 12, 2026

By submitting to men, tradwife proponents argue, a woman will activate his chivalric urge to protect and provide.

From Salon • Apr. 8, 2026

The couple had travelled from Houston to the Louisiana base to obtain a military ID for Ramos and activate her military spouse benefits, with plans to move her onto the base over Easter weekend.

From BBC • Apr. 7, 2026

But Leo still had to deduce the right sequence to activate this control sphere.

From "The Mark of Athena" by Rick Riordan

Related Words

• call up
• mobilize
• stimulate
• switch on
• trigger
• turn on