Which HTML tag is specifically designed for defining important text?

The <strong> tag is specifically designed to denote text that is of strong importance. It semantically indicates that the enclosed text has greater significance than surrounding text. This is not only crucial for visually conveying importance through default styling (often bolded), but it also enhances accessibility for screen readers and search engines, as they can recognize the emphasis on the content.

In contrast, the <b> tag simply styles text to appear bold without indicating any semantic importance, which means it doesn’t carry additional meaning beyond the visual effect. The <em> tag indicates emphasis on text, implying importance, but it's generally used for slightly different purposes, like expressing a change in tone. Similarly, the <i> tag is used for italicization, often for stylistic purposes, such as marking non-English phrases or titles, without imparting any emphasis on importance or meaning. Thus, using the <strong> tag is best practice when conveying important information in HTML.