In the following question, names of common plane figures are given. Three of them are specific types of quadrilaterals, while one is a general term that can have any number of sides. Select the figure which is different from the other three (odd one out).

Introduction / Context:
This is a conceptual geometry question from aptitude that checks your understanding of basic plane figures. You are given several shape names and asked to identify which one does not belong to the same specific group. Recognising the difference between special quadrilaterals and a broad geometric category is useful for school mathematics as well as many competitive exams.

Given Data / Assumptions:
- The options are Square, Rectangle, Rhombus, Polygon, and Parallelogram.
- Square, Rectangle, Rhombus, and Parallelogram are all specific types of quadrilaterals with four sides.
- The term Polygon is a general word that refers to any closed figure made of straight line segments with three or more sides.
- Exactly one option is not a specific quadrilateral type and will be the odd one out.

Concept / Approach:
The key idea is to classify each figure by the number of sides and by how specific the definition is. Quadrilaterals have exactly four sides. A Square is a special quadrilateral with all sides equal and all angles right angles. A Rectangle has opposite sides equal and all angles right angles. A Rhombus has all sides equal but angles need not be right angles. A Parallelogram has opposite sides parallel and equal. In contrast, Polygon is a very general term that describes any many sided figure, not just four sided ones, so it stands apart from the rest.

Step-by-Step Solution:
Step 1: A Square is a quadrilateral with four equal sides and four right angles.Step 2: A Rectangle is a quadrilateral with opposite sides equal and four right angles.Step 3: A Rhombus is a quadrilateral with all sides equal but angles are not fixed to 90 degrees.Step 4: A Parallelogram is a quadrilateral with opposite sides parallel and equal in length.Step 5: Polygon is any closed plane figure made from straight line segments with three or more sides; examples include triangles, pentagons, hexagons, and quadrilaterals.Step 6: Since Polygon is a broad category that includes many shapes and is not restricted to four sided figures, it is different from the other specific quadrilaterals.

Verification / Alternative check:
You can also visualise the hierarchy of figures. All Squares, Rectangles, Rhombuses, and Parallelograms are quadrilaterals, and at the same time all quadrilaterals are polygons. So four options are special cases within the polygon family, but only Polygon is the parent category. The parent category is more general and therefore naturally becomes the odd one out among its specific subtypes.

Why Other Options Are Wrong:
Square is not the odd one out because it is a clear, specific type of quadrilateral. Rectangle is also a specific quadrilateral with well defined properties. Rhombus and Parallelogram are again special quadrilaterals with four sides and distinct geometric definitions. Since these four names describe particular types of quadrilaterals, they form one group and cannot be treated as the odd term in this list.

Common Pitfalls:
Some learners confuse Polygon with Quadrilateral and think both are equally specific. However, a quadrilateral is a polygon with exactly four sides, whereas Polygon is more general and can have three, four, five, or more sides. Remembering this hierarchy is helpful when dealing with classification questions. Always check whether a word is a broad family name or a very specific member of that family.

Final Answer:
Polygon