Small-print annotation alongside a word indicating its pronunciation or meaning. The normal case being furigana, where you have kana over a kanji word indicating the pronunciation. In this case, though, the ruby is in kanji, and explicating what the katakana word モルモット (guinea pig) signifies to Kaguya and Eirin respectively. (The term "ruby" comes from an old printers' term for the small type used.)
A visual cue to a word, phrase or symbol's pronunciation/reading. In other images, both in translation and the original, where a word has a smaller string of characters above or next to it, it's a guide to pronunciation, known as a ruby. Sometimes it's played straight (e.g., here and here), simply to guide pronunciation of an unfamiliar kanji/compound. Frequently, it's played for laughs, as here. (The extra joke here, of course, is that a ruby, by definition, is a visual element; you can't hear the difference.)
I'd have translated it as "reading", but in English, that would have some ambiguity.
I'm surprised you haven't seen this mentioned when it's employed in other images. Danbooru coders even came up with the <ruby> tag script to allow quick coding of the effect.
A visual cue to a word, phrase or symbol's pronunciation/reading. In other images, both in translation and the original, where a word has a smaller string of characters above or next to it? It's a guide to pronunciation, known as a ruby. Sometimes it's played straight (e.g., here and here, simply to guide pronunciation of an unfamiliar kanji/compound. Frequently, it's played for laughs, as here. (The extra joke here, of course, is that a ruby, by definition, is a visual element; you can't hear the difference.
I'd have translated it as "reading", but in English, that would have some ambiguity.
I'm surprised you haven't seen this mentioned when it's employed in other images. Danbooru coders even came up with the <ruby> tag script to allow quick coding of the effect.
I've probably seen it but either never saw referred to as ruby text or never equated it to it. I am familiar with furigana, so go figure.
I've probably seen it but either never saw referred to as ruby text or never equated it to it. I am familiar with furigana, so go figure.
It's derived from the typographical unit ruby (US call it "agate", both are derived from an old practice of inscribing small figures/patterns on literal ruby and agate for seals), which is equivalent to 5.5 typographical points (you know, "5.5" when you pick a font size in a word processor), or about 1.81 mm.
Any font type with a height of a ruby can also be called a ruby (type). This size is often used for (interlinear, usually) annotations in printed media, since it's often considered the smallest possible font size for printing while remaining legible.
The Japanese adapted this practice for typeset furigana, but over time ruby came to be used to refer to the furigana (or any annotated glosses) themselves, regardless of font size or medium. Literary writers then begin to use ruby text "creatively" to indicate nonstandard pronunciation; this is often used for dramatic or comedic effect (like in this manga).
This term then got back-imported into English to refer to any annotations used to indicate the pronunciation of logographic characters. This use was further solidified when W3C published the Ruby Annotation specification for supplementing html text with ruby markup (which is why markup codes like those on Danbooru also call it "ruby").
