Which characteristic specifically describes a markup language?

A markup language is specifically characterized by its use of tags that surround text to describe desired formatting and structure. These tags provide a way to annotate text so that a computer can understand how to display or process that text. For example, in HTML, tags like <p> (for paragraphs) and <h1> (for headers) are used to structure web content. This characteristic allows users to define how different elements of the text should be presented visually or logically, without altering the actual content itself.

The other options do not accurately capture the essence of markup languages. While it's true that markup languages are influential in web design, they are not limited solely to it; they can also be used in various contexts, such as document formatting for typesetting. Markup languages do not define program behavior (which is a characteristic of programming languages) and are not restricted to handling only numerical data. Instead, they can handle a wide range of data types, including text, images, and multimedia content, making the first option the most accurate description.