необходимый и достаточный(In logic, necessity and sufficiency refer to the implicational relationships between statements. The assertion that one statement is a necessary and sufficient condition of another means that the former statement is true if and only if the latter is true. Wiki. Thus, the most crucial task in the design of an intermittent mechanism is how to produce the dwell time necessary and sufficient to accommodate the completion of a prescribed series of operations. Klimzo Alexander Demidov)
необходимое и достаточное условие(condition that without which nothing will happen and upon whose fulfillment there is no need for any other conditions (Logic). BED: a necessary and sufficient condition for the eradication of unemployment. OCDAlexander Demidov)
