Parallel lines are straight lines that are always the same distance apart. Hence, they never meet. A real-world example of parallel lines would be train tracks. Parallel lines may be shown on a coordinate grid and can be described by an equation; horizontal parallel lines will have equations of the form y = k, where k is a constant; vertical parallel lines will have equations of the form x = k; diagonal (oblique) parallel lines will have equations of the form y = mx + c, where the value of m is the same for all lines that are parallel. m is the gradient (slope) of these lines, so we would say that parallel lines have equal gradient.
In GCSE Mathematics, understanding parallel lines can help us deduce properties of, and identify, shapes, allowing us to solve a range of geometric problems.
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