Lines and curves

Some lines are straight. Some bend. That is the whole story — but it is enough to keep mathematicians busy for years.

Straight lines

A straight line goes in only one direction. If you draw it with a ruler, it stays perfectly flat. Two famous places to see straight lines:

• the edge of a book,
• the edge of a table.

A square has four straight lines around it. So does a rectangle. A triangle has three.

Curved lines

A curve bends. It does not have to make a full loop — even a single bend counts.

• The edge of a circle is one big curve.
• A smile is a curve.
• A river on a map is a curve.

Mix and match

Some shapes have only straight lines (square, triangle, rectangle). Some have only curves (circle). And some have both — like a half-moon, which has one straight line at the bottom and one curve on top.

Try it

Draw on paper:

• one straight line,
• one curve,
• a shape with three straight lines (a triangle!),
• a shape with one curve (a circle, or a half-moon if you can).

Show your drawings to someone — they will be impressed.

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