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

# Security Definition(d) (Production FIX API)

> SecurityDefinition(d) is the server response describing an instrument's contract terms and trading parameters on the Deribit production FIX API.

The Security Definition `d` message is used for the following:

* Accept the security defined in a [`Security Definition Request (c)`](/fix-api/production/security-definition-request) message with changes to the definition and/or identity of the security.
* Reject the security requested in a Security Definition Request message.

| Tag | Name | Type | Required | Comments |
| - | - | - | - | - |
| 320 | `SecurityReqID` | String | Yes | Request identifier |
| 322 | `SecurityResponseID` | String | Yes | Equal to the `SecurityReqID` |
| 323 | `SecurityResponseType` | int | Yes | Type of Security Definition response. <p>Valid values: <ul><li>`2` = accept security proposal with possible revisions as indicated in the message,</li> <li>`5` = reject proposal</li></ul></p> |
| 55 | `Symbol` | String | No | Common, "human understood" representation of the security |
| 48 | `SecurityID` | String | No | Takes precedence in identifying security to counterparty. |
| 22 | `SecurityIDSource` | String | No | `101` = Multi-cast identifier, `102` = Combo instrument identifier |
| 225 | `IssueDate` | UTCTimestamp | No | Creation timestamp |
| 873 | `DatedDate` | UTCTimestamp | No | State timestamp |
| 58 | `Text` | String | No | Explanatory text string |
| | Group `UnderlyingInstrument` | | | |
| 711 | `NoUnderlyings` | int | No | Number of underlying items in the group, if applicable. Underlying group is present in reply to [`Security Definition Request (c)`](/fix-api/production/security-definition-request) with `SecurityRequestType(321)` = 3 |
| =>311 | `UnderlyingSymbol` | String | No | Combo-instrument symbols in reply to [`Security Definition Request (c)`](/fix-api/production/security-definition-request) with `SecurityRequestType(321)` = 3 |
| 965 | `SecurityStatus` | String | No | Denotes the current state of the Instrument. <p>Valid values: <ul><li>`1` = Active, </li><li>`2` = Inactive, </li><li>`3` = RFQ, </li><li>`4` = Closed,</li> <li>`12` = Archivized</li></ul></p> |
| | Group `InstrmtLegGrp` | | | |
| 555 | `NoLegs` | int | Yes | Number of legs that make up the Security |
| =>600 | `LegSymbol` | String | No | Non-combo instrument name |
| =>623 | `LegRatioQty` | int | No | Positive or negative adjusted to the strategy definition |


## Related topics

- [Security Definition Request(c) (Production FIX API)](/fix-api/production/security-definition-request.md)
- [Deribit Production FIX API Overview](/fix-api/production/overview.md)
- [Security List(y) (Production FIX API)](/fix-api/production/security-list.md)
- [Security Status(f) (Production FIX API)](/fix-api/production/security-status.md)
- [Security Status Request(e) (Production FIX API)](/fix-api/production/security-status-request.md)