Weak definites in English have been widely studied as an example of when the definite article doesn’t contribute uniqueness (Aguilar-Guevara & Zwarts 2011; Aguilar-Guevara et al. 2014, among others). I take uniqueness to stem from the interaction between definiteness and number within the noun phrase. From this perspective, weak definites should be seen as a data point situated in the larger cross-literature on number. One particular phenomenon from the literature on number, the understudied class of the English bare institutional singulars (BISs), has been discovered to share several semantic properties with weak definiteness, namely number neutrality, referential deficiency, and lexical idiosyncrasy. In this chapter, I postulate a shared ...