Recently, some discussions came up about 32 bit vs. 64 bit implementations of operating systems.

While I was composing a message about this topic, I realized that I did not know if there was a correct term for the number of bits supported by an operating system.

For example, various versions of Solaris and Linux have 32bit and 64bit releases. Is the distinction "architecture"? In my experience, that has referred to chip types (Intel vs. PPC). Is it a "release"? Typically, I think of a release as a version number a consistent feature set, that might run on different architectures.

Maybe it is just "architecture", after all, even though a chip family might have used several different bit sizes over time, the chips themselves are different when you jump from 32bit to 64bit.