Indefinites are known to give rise to different scopal (specific vs non-specific) and epistemic (known vs unknown) uses. Farkas & Brasoveanu (2020) explained these specificity distinctions in terms of stability vs. variability in value assignments of the variable introduced by the indefinite. Typological research (Haspelmath 1997) showed that indefinites have different functional distributions with respect to these uses. In this work, we present a formal framework where Farkas & Brasoveanu (2020)’s ideas are rigorously formalized. We develop a two-sorted team semantics which integrates both scope and epistemic effects. We apply the framework to explain typological variety of indefinites, their restricted distribution and licensing conditions, and some diachronic developments of indefinite forms.