8.10 Clarify meaning of "variable"

From the spec:

> Execution of a C# program proceeds shall proceed such that the side effects of each executing thread are preserved at critical execution points. A side effect is defined as a read or write of a volatile field, a write to a non-volatile variable , [...]

What is meant by "variable" at the end of the quoted text compared with "field" in the preceding part of the same sentence? Are we including captured variables (which can't be declared volatile, and aren't fields) in the latter?