# firstGroup

> Whether this is the first trigger event between the two groups the shapes belong to. Always true when either shape has no group or the world has event grouping disallowed. This is only reliable when each group's shapes all belong to one body.

## Definition

* **Type:** Property
* **Namespace:** [Unity.U2D.Physics](/engine/6000.7/script-reference/unity/u2d/physics.md)
* **Assembly:** UnityEngine.PhysicsCore2DModule

```csharp
public bool firstGroup { get; }
```

### Remarks

See [PhysicsWorld.PhysicsGroup](/engine/6000.7/script-reference/unity/u2d/physics/physicsworld/physicsgroup.md), [\_physicsGroup](/engine/6000.7/script-reference/unity/u2d/physics/physicsshape/physicsgroup.md) and [\_eventGroupingAllowed](/engine/6000.7/script-reference/unity/u2d/physics/physicsworld/eventgroupingallowed.md).