I think "closure" is clear :-) The issue is more on "close over." Based on the definition you gave on closure, are you saying that close over means just the transport of the bindings out of the context? That would be the same as closure. I'm rather thinking of "close over" as expanding and using these bindings in a place or context that can cause consistency issues. In that case the use of "close over" in the text above is correct. But if "close over" and "closure" are supposed to mean the same thing, then yes, the text should rather say  "accessing mutable state within these closures is not problematic." Thanks!