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# system

The string that identifies the coding system that defines this clinical code.

```
var system: String { get }
```

## Discussion

The system is usually expressed as a URL from the [HL7 Terminology](https://terminology.hl7.org/).
For example, the RxNorm, a coding system for medications uses:
`http://www.nlm.nih.gov/research/umls/rxnorm`.

---

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