What are parallel lines?
Year 3 identifies pairs of parallel and perpendicular lines. Year 4 uses them to classify quadrilaterals. Below: what it means, a worked example, the mistake to watch for and an 11+ question.
The answer
Parallel lines are lines that stay the same distance apart and never meet, however far they go.
What it means
Railway tracks and the lines on writing paper are parallel.
In diagrams, parallel lines are marked with matching arrows. A second pair gets double arrows.
Parallel lines do not have to be the same length, and they do not have to be horizontal.
A worked example
How many pairs of parallel sides does a rectangle have?
- The top and bottom sides are parallel.
- The left and right sides are parallel too.
- So a rectangle has 2 pairs of parallel sides.
The common mistake
Thinking lines must be the same length, or level with the floor, to be parallel. Two sloping lines of different lengths are parallel if they always stay the same distance apart.
How it comes up in the 11+
How many pairs of parallel sides does a regular hexagon have?
Answer: 3
- A regular hexagon has 6 sides.
- Each side is parallel to the side opposite it.
- 6 ÷ 2 = 3 pairs.
Related words and practice
More maths words
Questions parents ask
Can parallel lines ever meet?
No. They stay exactly the same distance apart for ever, so they never cross or touch.
Are the two sides of a triangle ever parallel?
No. Every pair of sides in a triangle meets at a corner, so a triangle has no parallel sides.
Knowing the words is half of an 11+ maths question
11+ papers use maths vocabulary without explaining it. The free diagnostic checks maths, English and both kinds of reasoning, and shows what to practise next. No card is required.