The zone of possible agreement (ZOPA), in sales and negotiations, describes the intellectual zone between two parties where an agreement can be met which both parties can agree to. Within this zone, an agreement is possible. Outside of the zone, no amount of negotiation will yield an agreement.
For example, take a person willing to lend money at a certain interest rate over a certain period of time and a person wanting to borrow money at a certain rate. If both parties can agree a rate and period then a ZOPA can be established.
Though even when it appears that ZOPA is apparently zero some creative agreement could be found. For example when two people compete for one job. The ZOPA is apparently zero. The solution is to "enlarge the pie”. For example change job description so it will be enough place for job integration of two people.[1]