Is moment of inertia a scalar quantity?

Answer: Yes, moment of inertia is a scalar quantity.

The moment of inertia is a scalar quantity because it has magnitude but no direction in basic rotational mechanics. It represents the resistance of a body to changes in its rotational motion and depends on the mass distribution relative to the axis of rotation. Although it plays a key role in vector equations like torque and angular momentum, the value of moment of inertia itself is expressed as a scalar in standard cases.