Esri require - check out a sample:
Basemap gallery | ArcGIS API for JavaScript
require([
"esri/map", "esri/dijit/BasemapGallery", "esri/arcgis/utils",
"dojo/parser",
"dijit/layout/BorderContainer", "dijit/layout/ContentPane", "dijit/TitlePane",
"dojo/domReady!"
], function(
Map, BasemapGallery, arcgisUtils,
parser
) {
Just make sure the module order is the same! Here's some more info:
Working with Dojo | Guide | ArcGIS API for JavaScript
Note, in the example code, there were some modules not passed in the function - they were referenced in the front-end instead of in the script block.