The metric unit for measuring length is the metre, abbreviated as $m$.

In the metric system, the metre serves as the base unit of length. It is a fundamental component of the International System of Units (SI), which is utilized worldwide for both scientific and everyday measurements. The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole along a meridian passing through Paris. However, it has since been redefined with greater precision based on the speed of light.

For practical applications, the metric system employs a range of prefixes to indicate multiples and submultiples of the metre. For example, one kilometre ($km$) is equivalent to $1,000$ metres, making it particularly useful for measuring longer distances, such as the length of a road. In contrast, one centimetre ($cm$) is one-hundredth of a metre, and one millimetre ($mm$) is one-thousandth of a metre. These smaller units are ideal for measuring objects that require greater precision, such as the width of a pencil or the thickness of a book.

The widespread adoption of the metric system is largely due to its decimal-based structure, which simplifies calculations. For instance, converting between units typically involves multiplying or dividing by powers of ten, a process that is considerably more straightforward than the complex conversions often required in the imperial system. This ease of use is a key reason why the metric system is taught in schools and is prevalent in scientific research, engineering, and various other fields.

Grasping the concept of the metre and its related units is crucial for solving problems in GCSE Maths. Whether you are calculating the perimeter of a shape, determining the height of a building, or measuring the distance between two points, a solid understanding of metric units is essential.