Definition
Two or more straight lines that lie in the same plane and remain the same distance apart along their entire length, never meeting no matter how far they are extended.
Plain English
Lines that run side by side at a constant distance from each other and never cross.
Context Anchor
Seen in airport diagrams, runway and taxiway layouts, chart symbols, and descriptions of aircraft or ground paths that run alongside each other.
Derivation
From the Greek 'parallelos,' meaning 'beside one another.' The sense of two things running side by side without meeting carries directly into the geometric meaning.
Why Pilots Care
A pilot may need to recognize parallel lines when reading airport diagrams, identifying parallel runways, or understanding markings that show paths running side by side.
Analogy
Like the two rails of a railway track — always the same distance apart, always heading the same direction.
Intuition Check
Parallel does not mean simply “near each other.” The lines must stay the same distance apart and not cross.
Example Sentence 1
The edges of a runway are parallel lines, keeping a constant width from threshold to threshold.
Example Sentence 2
The controller cleared the aircraft to fly parallel tracks five miles apart during the approach sequence.