This paper aims to clarify the existence of `Reduced` NPs (henceforth RNPs) in English whose head nouns are missing, as in "... sequences like these φ...," "The following φ are further examples of ...," "The first φ to arrive was Betty ...", in comparison with other types of NPs. Underlying this is an assumption that every type of NPs except pronouns has its head noun in it in the underlying form. This paper shows that the occurrence of RNPs is semantically constrained by such relations as those of partiality, equality, comparison, sequentiality, and exemplification, among others. The paper attempts to reinterpret the suggested semantic constraints in terms of scalar relations for the generality and simplicity of exposition. As a result, for the felicitous RNPs, one condition is proposed which specifies the disallowance of the SUPERORDINATE-TO relation and, on the other hand, a tendency for the choice of the RNPs between the two related NPs which are in the COORDINATE-TO relation is suggested, specifying that the choice of the head to be omitted depends on sub-types of semantic relation.