What does the term 'flat iron' refer to?

The term 'flat iron' specifically refers to a heated tool used to straighten hair. This styling device typically features two flat plates that, when heated, can be clamped onto sections of hair to smoothen and straighten it. The heat effectively breaks down the hydrogen bonds in the hair, allowing it to be reshaped into a straighter form upon cooling. This makes flat irons a popular choice for achieving sleek, straight hairstyles and is widely used in salons and at home.

The other options describe different hair tools: devices for curling hair use a different mechanism (usually cylindrical) to create curls, while detangling brushes have bristles designed to ease knots in hair without pulling. Tools designed for drying hair, such as blow dryers, employ airflow and heat to remove moisture rather than directly straightening hair.