equivalences in/of $(\infty,1)$-categories
The analog in (∞,1)-category theory of epimorphism in category theory.
For $C$ an (∞,1)-category, a morphism $f : X \to Y$ in $C$ is an epimorphism if for all $A \in C$ the induced morphism
is a monomorphism in an (∞,1)-category in ∞Grpd.