Intervene (verb)

1. Come between so as to prevent a situation from developing or to limit its effects.
2. Take part in a situation in order to help or to prevent harm.
3. Occur or be placed between other things.

Origin:

Late middle english (in the sense 'come between two things'): from latin intervenire, from inter- 'between' + venire 'come'.

Examples:

1. The government decided to intervene in the conflict.
2. The police had to intervene to break up the fight.
3. Her friends tried to intervene and save her from making a mistake.
4. The doctor may have to intervene if the patient's condition worsens.
5. The meeting was intended to intervene in the negotiations and prevent further escalation.