Which language is specifically designed for defining the structure of a webpage?

The language specifically designed for defining the structure of a webpage is HTML, or HyperText Markup Language. HTML is the foundational markup language used to create the content and structure of web pages. It enables the organization of text, images, links, and other multimedia elements on the web. Through the use of various tags and elements, HTML outlines the hierarchy of information on a webpage, which web browsers interpret and render accordingly.

In contrast, CSS (Cascading Style Sheets) is used primarily for styling the visual presentation of the HTML content, allowing for improvements in layout, colors, and overall aesthetics, but it does not define the structure itself. JavaScript adds interactivity and dynamic behavior to web pages but is not used for structuring content. XML (eXtensible Markup Language) is a markup language designed to store and transport data, and while it can be used to create custom markup languages, it is not specifically aimed at defining webpage structure like HTML is. Thus, HTML is the correct answer as it is the core language for webpage structure.