It has been assumed that a null noun is present when a quantifier occurs by itself or precedes a partitive of-phrase. The claim is that the null noun corresponds to the pronoun one or a phonetically-deleted noun under identity (Hoeksema, 1984; Ionin et al., 2006). I argue that postulating a covert one or a deleted noun faces empirical problems, thereby further supporting the claim that a quantifier has two distinct functions in the lexicon?a nominal function and an adjectival/determiner function (Shin, 2007, 2016). The two functions of a quantifier can be captured in a systematic manner by means of morphological zero-derivation. By adopting a semantic composition approach to affixal morphology, I propose that nominal quantifiers can be derived from adjectival/determiner quantifiers by combining them with a null affix denoting a part-of relation in the quantity dimension.