The previous article looked at how Genkai changed the way words were arranged. This article looks at a second innovation — how words were explained.

Earlier dictionaries taught you kanji

Most wordbooks before the Edo period didn’t, in fact, explain a word’s meaning as such. Their role was closer to showing, for a given native Japanese word (read by its kun’yomi), the corresponding kanji. Look up “inu,” and you’d be shown the character 犬 — this is less an explanation of meaning than a guide to writing.

Genkai, by contrast, carried out one consistent task across its entire length for every single word: paraphrasing what that word means, in a different Japanese sentence. The function we now expect from a dictionary — a definition — genuinely begins in earnest here.

Down to pronunciation, accent, and part of speech

Genkai’s innovation doesn’t stop at definitions. As the overview article noted, Ōtsuki laid out this book’s design, item by item, in his own preface, “The Main Intent of This Book’s Compilation.” There, he lists, one after another, problems no one had yet tackled systematically: how to distinguish homographs pronounced differently, how to notate pitch accent, and how to indicate which part of speech — noun, verb, adjective, and so on — each word belongs to.

Headword arranged in gojūon order Pronunciation, accent notation distinguishing homographs Part of speech noun, verb, adjective, etc. Definition the meaning itself, paraphrased in Japanese Describing one word across four layers at once — this became the shape of a "modern dictionary"
The four layers of information Genkai attached to a single word. Diagram: ToL

Whoever invents the “obvious” gets forgotten

This basic dictionary design — presenting headword, pronunciation notation, part of speech, and definition together as one unit — is, today, something you take in without even noticing, every time you open a Japanese dictionary. But this “given” only came to exist because Ōtsuki worked it out, piece by piece, by feel, for the first time. There’s a well-known irony: once an invention truly succeeds, people forget it was ever an invention at all, and start treating it as simply “the obvious way.” Genkai’s basic design is, in exactly that sense, one of the most successful inventions there is.

Summary

PointDetail
Earlier dictionariesShowed the kanji corresponding to a native Japanese word — closer to a writing guide
Genkai’s methodParaphrased a word’s meaning in a different Japanese sentence (a definition)
Also built out at the same timeNotation for pronunciation and accent, a scheme for classifying parts of speech

In a nutshell — the almost absurdly simple idea of “explaining Japanese in Japanese” was, for the first time, carried out in earnest, across an entire dictionary, by Ōtsuki.