The most widely used term in negotiation is
BATNA. It stands for
Best Alternative To Negotiated Agreement. In simple words, it is your Plan B in negotiation. It is important to mention, that the term was introduced by two Harvard professors, Roger Fisher and William Ury, in their book "
Getting to Yes" in 1981. This book has established a major framework for a negotiation process that is widely used by all academics and practitioners today.
BATNA is your Plan B in case you don't achieve an agreement with your counterparty. The next question is, at what level are you ready to walk away from making the deal? The answer to this question will be your reserve price, minimum price (if you are a seller or maximum if you are a buyer) you are willing to accept to reach an agreement.
BATNA is the key in any negotiation tactic and should be determined before a negotiation takes place.