\underline{AB}The command \underline{AB} is used in LaTeX to create a horizontal line (underline) beneath the text or mathematical expression 'AB'. This is often used to emphasize or highlight specific parts of the text or equations.
Underlining part of an equation to emphasize it.
\underline{AB} + CD = EFUnderlining a vector symbol in text to highlight its importance.
\text{The vector } \underline{v} \text{ is important}Underlining a word in a sentence to draw attention to it.
\underline{\text{Note:}} \text{ This is crucial}