adjective
: of unavoidable importance : essential , indispensable
in politics, personality is very often of the essence — R.H.Rovere
in a revolution, timing is of the essence: temporary expedients are apt to congeal into permanent situations — Gladys Delmas
it is not enough to say that we are trying to equip young women for life in a self-governing country, though that is clearly of the essence — Smith College President's Report