In angularJS, having trouble instantiating main module - angularjs

Question

Every time I try to inject a dependency, I get this error:
Uncaught Error: [$injector:modulerr] Failed to instantiate module marbleApp due to:
Error: [$injector:modulerr] Failed to instantiate module ngRoute due to:
Error: [$injector:nomod] Module 'ngRoute' is not available! You either misspelled the module name or forgot to load it. If registering a module ensure that you specify the dependencies as the second argument.
I started with this, and my code ran fine:
var app = angular.module("marbleApp", []);
But then when I try to inject a dependency like this, I get the above error...
var app = angular.module("marbleApp", ["ngRoute"]);
Any thoughts on why this could be happening?

Answer 1

remember that you have to check two things when you want to inject some dependencies:
First:
var myModule = angular.module('myModule', [
'myDependency',
'mySecondDependency'
]);
Second:
myModule.config(['myDependency', 'mySecondDependency',
function(myDependency, mySecondDependency) {
//here you can use injected stuff
}
]);
Cheers!

Answer 2

Did you install angular-route, to start with?
$ bower install angular-route
If you want to update your bower.json, too:
$ bower install angular-route --save
More, as the comment from #ddepablo suggests, double check you have it added in your index.html file:
<script src="angular-route.js">
(see https://docs.angularjs.org/api/ngRoute)