What attribute is used to specify the language in the HTML tag?

The attribute used to specify the language in the HTML tag is "lang." This attribute provides essential information about the language of the content within the HTML document, which is crucial for search engines, screen readers, and other tools that process web pages. By indicating the language, it helps improve accessibility and ensures that the content is delivered in the correct linguistic context.

Using the "lang" attribute enhances the user experience, particularly for users with disabilities who rely on assistive technologies. In addition, it can influence how search engines index and present content. For example, if a webpage is primarily in Spanish, setting the lang attribute to "es" (for español) helps both users and search engines understand the primary language of that content.

The other potential attributes listed, such as "language," "code," and "locale," do not provide the same functionality or are not valid HTML attributes for defining the language of a document. Thus, "lang" is the appropriate and standardized way to convey this information in HTML.