Longman Dictionary of Contemporary English homepage

activate

 verb
     
ac‧tiv‧ate [transitive] technical
to make an electrical system or chemical process start working [≠ deactivate]:
Cooking fumes may activate the alarm.
The yeast's growth is activated by sugar and warmth.
—activation noun [uncountable]
Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.

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