A variable defined outside of a function may be what?

When a variable is defined outside of a function in Python, it is considered a global variable. Such variables can be accessed by any function within the same scope or module. While it is true that global variables can be read from within functions, modifying them directly requires declaring them as global within that function.

When a variable is read, it means the function can use its value in calculations or logic. However, without the global keyword, the variable cannot be modified or written to directly within that function; any assignment statements would create a new local variable instead of affecting the global one. This is why saying that a variable defined outside of a function may only be read (but not written) is accurate.

In this context, options that suggest writing to the variable (like writing only or written and read) do not acknowledge this crucial aspect of variable scope, while the option regarding deletion pertains to another kind of operation entirely, which can be done regardless of the variable's global status.