GameObject.SendMessage
SendMessage(methodName: string, value: object = null, options: SendMessageOptions = SendMessageOptions.RequireReceiver): void;
void SendMessage(string methodName, object value = null, SendMessageOptions options = SendMessageOptions.RequireReceiver);
def SendMessage(methodName as string, value as object = null, options as SendMessageOptions = SendMessageOptions.RequireReceiver) as void
Parameters

methodName The name of the method to call.
value An optional parameter value to pass to the called method.
options Should an error be raised if the method doesn't exist on the target object?
Description

Calls the method named methodName on every MonoBehaviour in this game object.

The receiving method can choose to ignore the argument by having zero parameters. If options is set to SendMessageOptions.RequireReceiver an error is printed if the message is not picked up by any component.

Note that messages will not be sent to inactive objects (ie, those that have been deactivated in the editor or with the SetActive function).
	// Calls the function ApplyDamage with a value of 5
	gameObject.SendMessage ("ApplyDamage", 5.0);
	
	// Every script attached to the game object 
	// that has an ApplyDamage function will be called.
	function ApplyDamage (damage : float) {
		print (damage);
	}
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void ApplyDamage(float damage) {
        print(damage);
    }
    void Example() {
        gameObject.SendMessage("ApplyDamage", 5.0F);
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def ApplyDamage(damage as float) as void:
		print(damage)

	def Example() as void:
		gameObject.SendMessage('ApplyDamage', 5.0F)