From the given definitions, let's match each of them to the correct terms.
• Circle:
Set of points in a plane that are equidistant from a given point.
• Sector:
This is the region of a circle bounded by an arc and two radii.
• Tangent:
A line that intersects the circle in exactly one point.
• Radians:
Another way to measure angles using the ratio arc length/radius.
• Arc:
The part of a circle lying between two points on the circle.
• Chord:
A line segment whose endpoints are on the circle.
• Circumcenter:
This is the intersection of all three perpendicular bisectors of a triangle's side and the center of the triangle.
• Circumscribed polygon:
Polygon in which all sides are tangent to an inscribed circle.
• Circumscribed circle:
Circle about a polygon in which all vertices intersect the circle.
• Inscribed angle:
An angle formed by two chords in a circle that share the same endpoints.
From the above, we have matched the definitions to the correct terms.