What is synonym for effective?

Here are some synonyms for "effective," depending on the context:

General:

* Successful

* Productive

* Efficient

* Powerful

* Potent

* Fruitful

* Working

* Operative

* Achievable

Formal:

* efficacious

* effectual

* operative

* potent

* viable

Informal:

* good

* strong

* working

* getting the job done

* hitting the mark

More specific:

* For communication: Persuasive, clear, impactful

* For solutions: Practical, feasible, viable

* For treatment: Curative, remedial, therapeutic

* For weapons: Lethal, destructive, powerful

The best synonym depends on the specific context and the nuance you want to convey.