In set theory, AD+'s an extension, proposed by W. Hugh Woodin, to the axiom of determinacy. The axiom, which's to be understood in the context of ZF plus DCR (the axiom of dependent choice for reals), states two things:# Every set of reals's ∞-Borel. For any ordinal λ less than Θ, any subset A of ωω, and any continuous function π:λω→ωω, the preimage π-1[A]'s determined. (Here λω's to be given the product topology, starting… (More on Ad)