General opposite:
* Allow
* Permit
* Enable
* Facilitate
More specific opposites:
* Cause (if "prevent" means to stop something from happening)
* Promote (if "prevent" means to stop something from growing or increasing)
* Encourage (if "prevent" means to stop something from happening)
* Support (if "prevent" means to stop something from happening)
Example:
* Prevent: "The fence prevents the dog from escaping."
* Opposite: "The open gate allows the dog to escape."
It's important to consider the specific context to determine the best opposite for "prevent."