| adjective | producing or capable of producing an intended result or having a striking effect; -LewisMumford “an air-cooled motor was more effective than a witch's broomstick for rapid long-distance transportation” |
| adjective | having legal efficacy or force “a sound title to the property” |
| effect | verb | produce |
| effectiveness | noun | power to be effective; the quality of being able to bring about an effect |
| effectivity | noun | power to be effective; the quality of being able to bring about an effect |
| effectualness | noun | power to be effective; the quality of being able to bring about an effect |
| effectuality | noun | power to be effective; the quality of being able to bring about an effect |
| efficacy | noun | capacity or power to produce a desired effect |
| efficaciousness | noun | capacity or power to produce a desired effect |
| legality | noun | lawfulness by virtue of conformity to a legal statute |