Give a definition for perpendicular lines. Are there other terms that need to be defined first? What are they,and how might you define them?

(N/A) Perpendicular lines: Two lines $p$ and $q$ lying in the same plane are said to be perpendicular if they intersect at a right angle $(90^{\circ})$,and we write them as $p \perp q$.
Yes,there are other terms that need to be defined first:
$1$. Line: $A$ line is a breadthless length that extends indefinitely in both directions.
$2$. Plane: $A$ surface which has only length and breadth.
$3$. Angle: The inclination between two intersecting lines.
$4$. Right angle: An angle whose measure is $90^{\circ}$.