Русско-англо-русский юридический словарь

Two parties purport to "agree" to have concluded a contract for a car, but have not actually worked out a price, it cannot be said that they have concluded a contract. The price would seem to be an "essential term". If further, the "buyer" had gone to a car dealer and said he would pay £10,000 for a car, but has not said which car, a "essential term" is probably lacking again. The price and the thing exchanged are examples of essential terms in simple sale of goods contracts. (Wikipedia)

essential term (of a contract) – a provision required for a contract to exist. The client must give informed consent in writing to both the essential terms of the transaction and the lawyer's role in it. (translegal.com)