Which tag defines a list item in both ordered and unordered lists?

The tag that defines a list item in both ordered and unordered lists is the "Li Tag." This tag is essential for creating lists in HTML, as it is used to encapsulate individual list items within either a bulleted list or a numbered list.

In the context of HTML coding, when you are creating an unordered list, you use the "Ul Tag" to define the list itself, and each list item is wrapped in an "Li Tag." Similarly, when creating an ordered list, the "Ol Tag" serves the same purpose, allowing you to number the list items, with each item still being defined by the "Li Tag." Thus, the "Li Tag" is the common element that applies to both types of lists, making it the correct answer for identifying individual items within any list structure in HTML.