 (ii) These different kinds of metaphysical necessity are the counterparts of two types of entailment which Avicenna calls containment and necessary implication and which express necessary connections of different strength between terms. Containment is the relation between a notion and its intensional parts (i.e., the constituents of its definition, which are ontologically part of its essence). Necessary implication is a weaker form of necessity holding between two notions that are merely inseparable.