> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fluidinference.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Custom Pronunciation

> Override TTS pronunciation with custom lexicon files.

## Overview

FluidAudio TTS supports custom pronunciation dictionaries that override how specific words are pronounced. Essential for domain-specific terminology, brand names, acronyms, and proper nouns.

### Priority Order

1. Per-word phonetic overrides — Inline markup like `[word](/phonemes/)`
2. Custom lexicon — Your `word=phonemes` file entries
3. Case-sensitive built-in lexicon
4. Standard built-in lexicon
5. Grapheme-to-phoneme (G2P) — eSpeak-NG fallback

## File Format

```text theme={null}
# This is a comment
kokoro=kəkˈɔɹO
NASDAQ=nˈæzdæk
UN=junˈaɪtᵻd nˈeɪʃənz
```

Phonemes are compact IPA strings. Use whitespace to separate words in multi-word expansions.

## Word Matching

Three-tier strategy:

1. **Exact match** — `NASDAQ` matches only `NASDAQ`
2. **Case-insensitive** — `nasdaq` matches `NASDAQ`, `Nasdaq`
3. **Normalized** — Strips to letters/digits/apostrophes, lowercased

## Usage

### CLI

```bash theme={null}
swift run fluidaudio tts "The NASDAQ index rose today" \
  --lexicon custom.txt --output output.wav
```

### Swift API

```swift theme={null}
let lexicon = try TtsCustomLexicon.load(from: fileURL)

let manager = TtSManager(customLexicon: lexicon)
try await manager.initialize()
let audio = try await manager.synthesize(text: "Welcome to Kokoro TTS")

// Update at runtime
manager.setCustomLexicon(newLexicon)
```

### Merging Lexicons

```swift theme={null}
let combined = baseLexicon.merged(with: domainLexicon)
```

## Example Lexicon

```text theme={null}
# Finance
NASDAQ=nˈæzdæk
EBITDA=iːbˈɪtdɑː

# Technology
NVIDIA=ɛnvˈɪdiə
Kubernetes=kuːbɚnˈɛtiːz

# Product Names
Kokoro=kəkˈɔɹO
FluidAudio=flˈuːɪd ˈɔːdioʊ
```