# gt-node: General Translation Node.js SDK: derive
URL: https://generaltranslation.com/en-US/docs/node/reference/functions/derive.mdx
Docs index: https://generaltranslation.com/llms.txt
Description: Mark computed content as derivable for General Translation extraction. API reference for derive.

Derivable content is computed in source code but resolves to a fixed set of values the CLI can translate. Use `derive` when a translated string interpolates a value that should be discovered during extraction rather than treated as a runtime variable.

## Overview [#overview]

Wrap a computed expression with `derive` inside a translated string. The CLI resolves the expression into every possible static value and includes those values in the source content to translate. At runtime, `derive` returns its argument unchanged.

```ts
import { derive, getGT } from 'gt-node';

const gt = await getGT();
const message = gt(`My name is ${derive(getSubject())}`);
```

Signature:

```ts
derive<T extends string | boolean | number | null | undefined>(content: T): T
```

*Note: `derive` is a compile-time marker. Run [`gt validate`](/docs/cli/reference/commands/validate) after adding or changing `derive` calls to confirm the CLI can resolve each derivable expression.*

## How it works [#how-it-works]

- **Extraction hint.** The CLI attempts to resolve the wrapped expression into all of its possible static values and adds them to the content sent for translation.
- **Runtime passthrough.** At runtime, `derive` returns exactly what it received, so it has no effect on the value.
- **Non-derivable values.** When an expression cannot be statically analyzed, wrap it with [`declareVar`](/docs/node/reference/functions/declare-var) inside the `derive` call.

## Parameters [#parameters]

| Parameter | Description | Type | Optional | Default |
| --- | --- | --- | --- | --- |
| [`content`](#content) | The content to mark as derivable. | `string \| boolean \| number \| null \| undefined` | No | — |

### `content` [#content]

**Type** `string | boolean | number | null | undefined` · **Required**

The content to mark as derivable for translation extraction.

## Returns [#returns]

**Type** `T`

The same content, unchanged at runtime.

## Examples [#examples]

```ts
import { derive, getGT } from 'gt-node';

function getSubject() {
  return Math.random() > 0.5 ? 'Alice' : 'Brian';
}

const gt = await getGT();
const greeting = gt(`My name is ${derive(getSubject())}`);
```

## Notes [#notes]

- `derive` only affects extraction; it never changes the runtime value.
- Pair with [`declareVar`](/docs/node/reference/functions/declare-var) for values that cannot be statically resolved.

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