Quick Distinction: tiara vs circlet

In tagging a to-be-doomed post, I ran into a personal conflict: What's a tiara and what's a circlet? Many of the Sailor Moon images are tagged as tiaras, though they're the metal forehead-spanning bands (post #1001122 was tagged as such), but then when comparing with a search for circlet, post #1004750 came up, even though it's one of the semi-circular, sitting-on-your-hair crowns.

Just wanna know if I'm on the right track, or if how things currently are is what they should remain.

Tiaras sit on top of your head.
Circlets go around your head.

Alrighty then! Time to abuse the "Edit tag script" feature.

Before you "abuse" anything, I would only go for the most obvious examples, such as Sailor Moon tiara-to-circlet, and things like post #1004750 to tiara. After looking through some tiara and circlet posts, there are a lot of borderline examples that require a keener eye.

Yeah, my method is usually to apply them the cases I can tell from the thumbnails (usually close-ups and/or solos), and then open the iffy ones in new tabs.

About Sailor Moon, IIRC the things are officially called tiara there.

After mulling about it some more, I'm not too sure about the Sailor Moon accessories being circlets anymore. Circlets are, well, circular, while tiaras are semi-circular, and I don't see any part of the Sailor Moon accessories reaching beyond the characters' ears.

Haven't been on in a couple days to rifle through the posts, but it still doesn't sit well with me, since I've never considered tiaras as sitting much lower than on top of your head. Perhaps a more descriptive wiki, with numbered bullets for the different styles tagged?