Which of the following is an example of an undefined notion?

Question

An angle is an example of an undefined notion.
A line segment is an example of an undefined notion.
A circle is an undefined notion.
A line is an example of an undefined notion.

Answer 1

In geometry, an "undefined notion" refers to basic concepts that are not formally defined using other terms but are understood intuitively. Among the options provided, the following concepts are typically considered undefined notions:

• A point
• A line
• A plane

Of the options you provided, a line is commonly considered an undefined notion in geometry.

So, the correct answer is "A line is an example of an undefined notion."