Odd One Out — Arc, Diameter, and Tangent are circle-specific terms; Diagonal primarily belongs to polygons (e.g., quadrilaterals). Identify the odd geometric term.

Introduction / Context:
Geometric vocabulary can be grouped by the shapes they belong to. Three terms are standard circle concepts; one belongs to polygons.

Given Data / Assumptions:

• Arc: a portion of a circle.
• Diameter: a chord through the center of a circle with length 2*radius.
• Tangent: a line touching a circle at exactly one point.
• Diagonal: line segment joining non-adjacent vertices of a polygon; circles have no vertices.

Concept / Approach:
Assign each term to its natural geometric context and select the one not specific to circles.

Step-by-Step Solution:
Arc → circle term.Diameter → circle term.Tangent → circle term.Diagonal → polygon term → outlier.

Verification / Alternative check:
Ask: can the term be defined without reference to vertices? Circle terms do; a diagonal requires vertices (absent in circles).

Why Other Options Are Wrong:

• Arc, Diameter, Tangent: canonical circle terminology.

Common Pitfalls:
Confusing “chord” and “diameter” vs “diagonal.” A chord/diameter is inside a circle; a diagonal is a polygon construct.

Final Answer:
Diagonal