A more thorough explanation:

Definition: An intervenor is a person who voluntarily enters a lawsuit that is already in progress because they have a personal interest in the outcome of the case. This person is also known as an intervener.

Example: Let's say that a company is being sued for polluting a river. An environmental group that has a vested interest in protecting the river may choose to become an intervenor in the lawsuit. By doing so, they can participate in the legal proceedings and advocate for their interests.

Explanation: In this example, the environmental group has a personal stake in the outcome of the lawsuit because they are concerned about the impact of the pollution on the river. By becoming an intervenor, they can make sure that their voice is heard and that their interests are taken into account during the legal process.