diff --git a/docs/voice-banned.txt b/docs/voice-banned.txt
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+# Words and phrases that do not go into anything a person reads here.
+# Why: docs/voice.md. The rule: docs/rfc-cleanup.md §2.10.
+#
+# One entry per line, written as it would appear in a sentence. Case does not
+# matter. An English entry matches whole words, so "here's" does not catch
+# "there's", and covers the word's other forms ("ensure" catches "ensures"
+# and "ensuring"). A Korean entry matches anywhere in the text. A line that
+# starts with # is a comment.
+#
+# check:voice (scripts/voice-lint.ts) reads this file. Adding a word needs no
+# change to the script.
+
+seamless
+robust
+leverage
+comprehensive
+streamline
+empower
+cutting-edge
+ensure
+utilize
+delve
+it's important to note
+here's
+
+효율적으로
+원활하게
+강력한
+최적화된
+혁신적인
+다양한
+전반적으로
+참고로
+살펴보겠습니다
diff --git a/docs/voice.md b/docs/voice.md
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+# Writing voice
+
+The README and the build guide set the voice for English here. Read a page of
+[README.md](../README.md) and of [BUILD_GUIDE.md](../BUILD_GUIDE.md) before
+writing anything longer than a sentence. Where the two differ, write like the
+README: it has no dash between clauses and no emoji callout, and the build
+guide still has both. Korean has a standard of its own, at the end.
+
+## Name the thing
+
+Not "the power input" but "`J4`, the screw terminal". Not "a lot of LEDs"
+but "8,192 points of light". A number carries its unit, and when it helps,
+the thing it is measured against:
+
+> it holds the panel to a 2.4 A budget, the high-power USB-A rating, so a
+> white-out frame lands at roughly half brightness instead, while an ordinary
+> bright pattern (~1.9 A) never notices.
+
+A part is named as the BOM names it (`PEC11R-4220F-S0024`), and a knob gets
+its place the first time: "K2, the top-left knob".
+
+## Say what happens
+
+The guides say what the reader will see, and what it means when it looks
+wrong: "The dialog usually ends without asking for it, and nothing failed:
+close it." A limit is stated as one, even after a fix: "1/120 and slow motion
+still band". "Usually" appears where it is true and the reader can act on it,
+not as a cushion under every sentence.
+
+## Short, and finished
+
+Sentences carry one point each. A long one is followed by a short one, and a
+short one can open a section by itself: "Two licenses, in two separate
+files." A step starts with what to do and then says why: "Buy the LED panel
+the BOM links. It's verified, and the case is measured around its screw
+holes." A paragraph covers one thing and stops when it is said.
+
+## Who is speaking
+
+"You" is the reader. "We" is everyone who makes Patternflow: "Every
+Patternflow plays every pattern we make." "I" is SeungHun Lee, only on a page
+that already speaks as him, and only for something he does: "I'll add your
+pin to the build map." New text never gives him a memory or a feeling he did
+not write himself.
+
+## Words with fixed meanings
+
+[EDITIONS.md](EDITIONS.md#the-three-words) defines the words for firmware
+builds, and prose uses them as defined there. A bundle is a composition's
+folder and nothing more; "addon" and "variant" stay only where they name the
+wire. Brand spelling is hard rule 4 in [AGENTS.md](../AGENTS.md).
+
+## Side by side
+
+A sentence that reads as generated, then the one the README has instead:
+
+> Make sure to select the correct USB port, as using the wrong one may cause
+> problems during setup.
+>
+> Use its left port, labelled `USB` (antenna up, ports toward you): the right
+> one flashes too, but the Wi-Fi step never appears there.
+
+## Korean
+
+Korean keeps the ending its file already uses (해요체 or 합니다체) and reads
+as if it was written in Korean first. Everything above holds in Korean too.
+Neither the journal nor the web guide is the model. The journal is a diary,
+and the guide's Korean was carried over from its English sentence by
+sentence. The marks of carried-over Korean, as two published Korean editing
+skills list them (DaleSeo's
+[humanizer](https://github.com/DaleSeo/korean-skills/tree/main/skills/humanizer)
+and epoko77-ai's [Humanize KR](https://github.com/epoko77-ai/im-not-ai)):
+
+- English prepositions turned into particles: `~에 대해`, `~를 통해`,
+  `~에 있어서`, `~에 의해`. The plain particle or the verb says it.
+- An English verb on a subject that is not a person. "드라이버 IC가
+  결정해요" is "the driver IC decides".
+- `가지고 있다` for have, and `~되어지다` for a passive that `~되다`
+  already is.
+- `~할 수 있다` where the sentence can simply say the thing.
+- A noun doing a verb's work: `확인을 진행해요` for `확인해요`.
+- Pronouns and plurals the sentence does not need: `그`, `그것`, `이러한`,
+  `-들`.
+- A comma wherever English would put one. Korean uses fewer
+  ([KatFishNet](https://aclanthology.org/2025.acl-long.1030/), ACL 2025).
+
+Two of the guide's lines in English and in Korean, then the same thing
+written in Korean:
+
+> Its driver IC decides, not “HUB75E” in the title.
+>
+> 제목의 ‘HUB75E’가 아니라 드라이버 IC가 결정해요.
+>
+> 패널이 켜질지는 제목의 ‘HUB75E’가 아니라 드라이버 IC에 달려 있어요.
+
+> Take $100 as the floor, not the estimate
+>
+> 100달러는 예상치가 아니라 바닥이에요.
+>
+> 100달러는 아무 문제 없이 끝났을 때 드는 돈이에요. 보통은 더 들어요.
+
+Words that never go in are in [voice-banned.txt](voice-banned.txt), one per
+line. The maintainer adds to it, and `check:voice` reads it from there once
+it lands ([rfc-cleanup.md §2.10](rfc-cleanup.md#210-writing-voice)). A
+sentence that needs one of them to stand up is a sentence to cut.