Can "furigana" be used to refer to ruby that isn't kana?

In English, the term ruby refers to small text set above the main text (in horizontal writing) or to the right of the main text (in vertical writing). From Wikipedia:

Ruby characters (ルビ) are small, annotative glosses that can be placed above or to the right of a Chinese character when writing languages with logographic characters such as Chinese or Japanese to show the pronunciation. Typically called just ruby or rubi, such annotations are used as pronunciation guides for characters that are likely to be unfamiliar to the reader.

As I understand it, this is mainly a typography term, and it's likely that many speakers are unfamiliar with it, but web developers probably know the term due to the HTML tag. Students of Japanese are more likely to know furigana than ruby.

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In Japanese, although ルビ is used, I think that 振{ふ}り仮名{がな} is a much more common word. Taken literally, 振り仮名 appears to refer specifically to kana, as in hiragana or katakana. That would make ルビ a more general term, including small kanji or rōmaji used as ruby.

In fact, I've seen the term 振{ふ}り漢字{かんじ} used on occasion, in contrast to 振{ふ}り仮名{がな}:

kanji printed as ruby, usually to explain kana

My feeling is that taken strictly, 振{ふ}り仮名{がな} should only refer to kana used as ruby, not to kanji or rōmaji. But I'm not sure if that reflects actual usage, so I've decided to ask this question:

Is it common to use the term 振{ふ}り仮名{がな} for ruby text, even when the characters aren't kana?

(And if so, would that be considered sloppy usage, or would it be perfectly normal / acceptable?)

Answer

ルビ is originally a technical term of the publishing industries. The ruby feature is called ルビ in Adobe InDesign, MS Word, etc. A ruby can be in kana, kanji or even alphabets, but 傍点（圏点） is different from ruby. I suppose the word ルビ focuses more on the technical aspect of this feature.

And the word ふりがな focuses on the role of ルビ. It implies "how to read this out loud."

Because I know both of the two words, I would definitely avoid using ふりがな for rubies in non-kana characters, or rubies for "double meaning" as in "[校長先生]{ストーカー}" or something. (Such rubies are occasionally seen in manga or 'light novels'). Not all Japanese recognize the term ルビ, so other people may call them ふりがな.

To be honest, I've never seen 振り漢字.