Clear definitions of lesser, greater, minor, etc.?

[Phalimar]

Is there a clear definition of the terms minor, lesser, moderate, greater, major, supreme and what they indicate? For example, a Sturdy Shield (CR588) shows a greater shield is Level 13 but a greater Staff of Transmutation (CR595) is listed as Level 10. A quick search on AoE http://2e.aonprd.com/Search.aspx?query=Lesser%20greater) returns lots of results but there doesn't appear to be a formal description of how to think of these terms? Are they simply a generalized relative scale?

[HammerJack]

I'm not sure what kind of formal definition you're looking for. They're modifiers that are generally used to differentiate different levels of related items. They don't carry any special rules significance.

[Razgriz 1]

These terms are relative to each other, not to a certain level. As long as you don't find a lesser staff of transmutation that's stronger than a greater staff of transmutation it's fine.

[Phalimar]

So it's just a way to identify relative power between the items in question. Thanks HammerJack and Razgriz1.