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Why are asteroids also called minor planets?

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Illustration showing a massive asteroid above a city map with a dinosaur silhouette for scale, highlighting the asteroid's size compared to major urban areas. — Asteroid This rock would take out more than just a *T. rex*.

Asteroids are called minor planets primarily due to their small size and large numbers relative to the major planets in our solar system.1

The terms "asteroid" and "minor planet" are often used interchangeably, though their usage can depend on the context of the research. Scientists who study groups of objects with similar orbital characteristics or those with dynamically interesting orbits often prefer the term "minor planet," while those focusing on the physical properties of these bodies typically use "asteroid".1

Historically, the term "asteroid" (meaning "starlike") was proposed by William Herschel after the discovery of objects like Ceres and Pallas, as he felt they were not large enough to be considered true planets. Today, the International Astronomical Union officially classifies these objects based on their characteristics; for instance, those massive enough to be rounded by their own gravity are designated as dwarf planets, while most smaller objects are officially categorized as "small solar system bodies," despite the continued informal use of the term asteroid.2