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# Glossary

> A glossary of voice and TTS terminology used across Onepin and the wider voice-AI field — TTS, STT, WER, MOS, prosody, phoneme, voice_map, and more, in plain language.

The voice field has a lot of shorthand. Here are the terms you'll meet most, defined plainly — with a pointer to where each one lives in Onepin when it does.

## The pipeline

**TTS (Text-to-Speech)** — Turning written text into spoken audio. The core of every run: the [Generator](/docs/workflow/generator) calls a TTS model to voice each line.

**STT (Speech-to-Text)** — The reverse of TTS: transcribing spoken audio back into text. Onepin uses STT inside the [Accuracy validator](/docs/workflow/accuracy-validator) to check that the generated audio actually said the script.

**Text normalization** — Rewriting text the way it's spoken before generation — "\$5" becomes "five dollars", "Dr." becomes "Doctor". The [Normalizer](/docs/workflow/normalizer) does this so numbers and symbols don't get read literally.

**voice\_map** — Onepin's per-language assignment of a voice and model inside the [Generator](/docs/workflow/generator). Each language maps to one or more voices.

**Provider** — The company behind a voice model — ElevenLabs, Cartesia, Naver, and others. Onepin routes to providers; you pick which voice each line uses. See [Voices & Models](/docs/get-started/voices-models).

**BYOK (Bring Your Own Key)** — Connecting your own provider account key to a workspace, so lines routed to that provider synthesize on your quota and your vendor bill instead of Onepin's — and cost `0` credits. Plan-gated, dashboard-managed. See [Bring your own key](/docs/guides/bring-your-own-key).

**Model ID** — A model's catalog identifier, like `eleven_multilingual_v2` or `sonic-preview`, as listed on [Voices & Models](/docs/get-started/voices-models). This is the value `voice_map` takes for `model`. The identifier that *does* trip people up is `voice_id` — see the [Generator](/docs/workflow/generator).

**Line** — One unit of script — a sentence or a row — that flows through the graph and becomes one piece of audio. Sometimes called a take.

**Locale / BCP-47** — The standard code for a language and region, like `en-us` or `ko-kr`. Onepin uses BCP-47 anywhere you set a language.

**SSML** — Speech Synthesis Markup Language: tags that tell a TTS model how to speak — pauses, emphasis, pronunciation. Some providers accept inline markup in the script.

## Quality and validation

**WER (Word Error Rate)** — How far a transcript strays from the intended words, as a percentage — the insertions, deletions, and substitutions over the total. Lower is better. Onepin reports the flip side, **word accuracy**, as the [Accuracy validator](/docs/workflow/accuracy-validator)'s score.

**MOS (Mean Opinion Score)** — A 1–5 rating of audio quality averaged across listeners — the long-standing yardstick for how good speech sounds. A naturalness score is a machine estimate of the same idea.

**Naturalness** — How human the speech sounds — its rhythm, stress, and flow — rather than whether the words are right. The [Naturalness validator](/docs/workflow/naturalness-validator) scores it 0–100.

**Prosody** — The melody of speech: pitch, pace, stress, and pauses. Good prosody is what separates a flat read from a natural one.

**Phoneme** — The smallest unit of sound in a language — the "k" in "cat". TTS models build speech from phonemes, and pronunciation dictionaries steer them.

**Threshold** — The score a line must reach to pass a [validator](/docs/workflow/validators). You set the bar; Onepin holds it.

**Retry** — Regenerating a line that failed a validator, up to a set budget, then delivering the best attempt. See [validators](/docs/workflow/validators).

## Related

* [Voices & Models](/docs/get-started/voices-models) — the model catalog
* [Workflow](/docs/workflow/overview) — the nodes these terms map to
* [Validators](/docs/workflow/validators) — accuracy, naturalness, and noise checks

> Onepin is a voice workflow platform that orchestrates, validates, and ships production-ready audio across 33 TTS models.