# Coroutine

> MonoBehaviour.StartCoroutine returns a Coroutine. Instances of this class are only used to reference these coroutines, and do not hold any exposed properties or functions.

## Definition

* **Type:** Class
* **Namespace:** [UnityEngine](/engine/6000.0/script-reference/unityengine.md)
* **Assembly:** UnityEngine.CoreModule
* **Inherits from:** [YieldInstruction](/engine/6000.0/script-reference/unityengine/yieldinstruction.md)

```csharp
public sealed class Coroutine : YieldInstruction
```

## Remarks

A coroutine is a function that can suspend its execution (yield) until the given [YieldInstruction](/engine/6000.0/script-reference/unityengine/yieldinstruction.md) finishes.

```csharp
using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    IEnumerator WaitAndPrint()
    {
        // suspend execution for 5 seconds
        yield return new WaitForSeconds(5);
        print("WaitAndPrint " + Time.time);
    }

    IEnumerator Start()
    {
        print("Starting " + Time.time);

        // Start function WaitAndPrint as a coroutine
        yield return StartCoroutine("WaitAndPrint");
        print("Done " + Time.time);
    }
}
```

This example shows a normal Start:

```csharp
using UnityEngine;
using System.Collections;

// In this example we show how to invoke a coroutine and execute
// the function in parallel.  Start does not need IEnumerator.

public class ExampleClass : MonoBehaviour
{
    private IEnumerator coroutine;

    void Start()
    {
        // - After 0 seconds, prints "Starting 0.0 seconds"
        // - After 0 seconds, prints "Coroutine started"
        // - After 2 seconds, prints "Coroutine ended: 2.0 seconds"
        print("Starting " + Time.time + " seconds");

        // Start function WaitAndPrint as a coroutine.

        coroutine = WaitAndPrint(2.0f);
        StartCoroutine(coroutine);

        print("Coroutine started");
    }

    private IEnumerator WaitAndPrint(float waitTime)
    {
        yield return new WaitForSeconds(waitTime);
        print("Coroutine ended: " + Time.time + " seconds");
    }
}
```