Parameters. Example: .block--mod or .block__elem--mod Modifier naming can also have a single dash. We already have a calc function in CSS that calculates the expression at the browser, Whereas calc in SASS is compile-time only. For class names using an established naming convention such as BEM, typically the Block and Element named classes are required as a minimum, with Modifiers typically being optional. border-radius: 5p With nesting, you can add classes between the braces of a declaration. This section of the document is included as a learning exercise to broaden the understanding about the origin of Class Composition. you can do this. but you have to create the css in the html document(not linked, but between the