Question

A line is an undefined term because it

Answer 1

LINE (an undefined term)
In geometry, a line has no thickness but its length extends in one dimension and goes on forever in both directions. Unless otherwise stated a line is drawn as a straight line with two arrowheads indicating that the line extends without end in both directions. A line is named by a single lowercase letter, , or by any two points on the line, .

Answer 2

http://www.regentsprep.org/Regents/math/geometry/GG1/undefinedterms.htm