\utilde{AB}The command \utilde{AB} is used to place an undertilde accent beneath the characters 'AB'. This is often used in mathematical notation to denote vectors or other entities that require a specific type of accentuation for clarity or emphasis.
Vector notation with undertilde accent
\utilde{AB}Bold vector with undertilde accent
\utilde{\mathbf{v}}Greek letters with undertilde accent
\utilde{\alpha\beta}