General antonyms:
* Cause: This is the most direct opposite, as cause and effect are linked.
* Origin: This focuses on the starting point rather than the result.
* Source: Similar to origin, this highlights the beginning of something.
Specific antonyms depending on the context:
* Ineffectiveness: If you're talking about the lack of an effect.
* Inefficacy: Similar to ineffectiveness, highlighting a lack of power to produce an effect.
* Failure: If you're talking about something that didn't achieve the desired effect.
* Lack: This highlights the absence of an effect.
Example:
* Effect: The new policy had a positive effect on employee morale.
* Antonym: The new policy had no effect on employee morale (lack).
It's important to consider the specific situation to choose the most appropriate antonym.