Final answer:
The undefined terms needed to define parallel lines are point and line. A point is a location without dimensions, while a line is a set of points that extends infinitely. Parallel lines never intersect and are always the same distance apart.
Step-by-step explanation:
In order to define parallel lines, we need the undefined terms point and line. A point is a location in space that has no dimensions, while a line is a set of points that extends infinitely in both directions. Parallel lines are lines that never intersect and are always the same distance apart.