The objective is to identify the geometric shape that is different from the others in the provided list.
The Square and Rectangle are both classified as quadrilaterals, meaning they have 4 sides. The Regular Hexagon has 6 sides.
The Isosceles triangle is the only shape listed that has 3 sides.
Based on the number of sides, the Isosceles triangle is distinctly different from the square, rectangle, and regular hexagon, making it the odd one out.