# Dictionary

Look up words while reading an EPUB using an offline StarDict dictionary stored on the SD card.

## Supported Format

The reader supports **StarDict** dictionaries. When searching for dictionaries online, look for "StarDict format" or files with `.dict`, `.idx`, and `.ifo` extensions.

A dictionary folder must contain:

- `.idx` — word index (required, **must be uncompressed** — a `.idx.gz` will not work; decompress it on your computer with `gzip -d` first)
- `.dict` or `.dict.dz` — definition data (`.dict.dz` is supported as-is; entries are decompressed on the fly during lookup)
- `.ifo` — metadata (optional)

Not supported: `.syn` synonym files (ignored), dictionaries with 64-bit index offsets (`idxoffsetbits=64` in the `.ifo` — rare, and rejected with an error), and HTML-formatted definitions render as raw markup rather than styled text.

## Setting Up a Dictionary

1. Copy your dictionary folder(s) to `/dictionaries/` on the SD card — one dictionary per folder, e.g. `/dictionaries/webster/webster.idx` + `webster.dict.dz`. A hidden `/.dictionaries/` folder (dot-prefixed) works the same way, for keeping it out of the file browser.
2. Open **Settings → Reader → Dictionary** on the device.
3. Select a dictionary from the list, or **None** to disable lookups.

The Dictionary setting only appears when at least one usable dictionary folder exists. Folders containing more than one dictionary (multiple `.idx` stems) are skipped as ambiguous.

## Looking Up a Word

Two ways to start a lookup while reading:

- Open the reader menu (**Confirm**) and choose **Look Up**.
- Or set **Settings → Controls → Long-press Menu** to "Dictionary", then hold **Confirm** (~0.4s) on the reading page.

One word on the page becomes highlighted:

1. Use **Left/Right** to move between words in reading order, and the side **Up/Down** buttons to jump between lines.
2. Press **Confirm** to look up the highlighted word.
3. Press **Back** to return to the reader.

On the very first lookup with a dictionary (and again if the dictionary file changes), the reader shows *"Indexing dictionary…"* while it builds a small `.qidx` sidecar file next to the `.idx`. This takes a few seconds for large dictionaries and makes all subsequent lookups fast. The sidecar can be deleted safely at any time — it will simply be rebuilt.

### How Lookup Works

1. **Direct match** — the word is found as-is (case-insensitive) in the dictionary index. Surrounding punctuation is ignored.
2. **Stemming** — on a miss, common English word forms are retried automatically: possessives and plurals (`dogs` → `dog`, `stories` → `story`) and verb endings (`walked` → `walk`, `running` → `run`, `making` → `make`).
3. **Not found** — a short popup appears and you return to word selection.

## The Definition Screen

When a word is found, the definition screen shows the matched headword at the top and the definition text below, with a page counter for long definitions.

- **Left/Right** or side **Up/Down** — previous / next page
- **Back** — return to word selection



## Where to find dictionaries

> credit to https://github.com/koreader/koreader/wiki/Dictionary-support for the list.

- The [reader.dict](https://www.reader-dict.com) (ex "BoboTiG/ebook-reader-dict") project provides StarDict version of daily dumps of [Wiktionary](https://www.wiktionary.org/) monolingual dictionaries for a variety of languages. It also provides [non-free multilingual](https://www.reader-dict.com) dictionaries.
- The [WikDict](https://www.wikdict.com) project provides free bilingual dictionaries based on [Wiktionary](https://www.wiktionary.org/) for a lot of language pairs. StarDict versions can be [downloaded from here](https://download.wikdict.com/dictionaries/stardict/).
- The [`Vuizur/Wiktionary-Dictionaries`](https://github.com/Vuizur/Wiktionary-Dictionaries) repository contains dictionaries based on [Wiktionary](https://www.wiktionary.org/) from many languages to English, including English-English.
- The [DictInfo](https://www.dictinfo.com/) website provides outdated monolingual dictionaries based on [Wiktionary](https://www.wiktionary.org/).
- The [Firedict site](https://tuxor1337.frama.io/firedict/dictionaries.html) contains a list of freely available dictionaries.
- [wiktionary_stardict](https://xxyzz.github.io/wiktionary_stardict/): update monthly.
- [Fictionaries](https://fictionary.gumroad.com/) provides dictionaries for various speculative fiction books and series.
- [World Factbooks Archive](https://github.com/MilkMp/CIA-World-Factbooks-Archive-1990-2025) provides 36 years of CIA's World Factbook dictionaries in StarDict format.
- [StarDict-Hebrew](https://github.com/Uri-Tauber/StarDict-Hebrew) Hebrew-English StarDict versions of Babylon dictionaries.