Abstract
Competition takes many forms. A newly identified type of competition involves the featural specification of one of the competitors as a key factor. In the particular instance treated here, whether a given item has a competitor depends on its number (and sometimes its person). We focus on the use of the genitive case versus adjective-like forms in possessive expressions (broadly understood). The data come primarily from the Slavonic languages, where a surprising original system of possessive pronouns competing with personal pronouns has played out rather differently through the family. We find a variety of outcomes, from conservative to highly innovative, with some instances of competitors settling into different niches.