Rock is a word with multiple related meanings in English. It commonly denotes a naturally occurring solid mass of minerals, but it is also used for a broad style of popular music and appears in everyday expressions and objects. Below are concise explanations of the principal senses of the term.

Rock (geology)

In geology, a rock is an aggregate of one or more minerals or mineraloids. Rocks form the solid outer layer of Earth and other terrestrial planets and are classified by their origin into three major groups:

  • Igneous rocks — form when molten material (magma or lava) cools and crystallizes. Examples include intrusive types that cool slowly beneath the surface and extrusive types that cool quickly after eruption.
  • Sedimentary rocks — result from the accumulation, compaction, and cementation of sediments. They often preserve fragments of older rocks, fossils, and layers that record past environments.
  • Metamorphic rocks — are rocks that have been transformed by heat, pressure, or chemically active fluids, changing their mineralogy and texture without melting.

Rocks are studied for what they reveal about Earth’s history, structure, and processes. They serve as raw materials in construction and industry (for example, crushed stone, building stone, and sources of metals and other resources). Important physical properties include mineral composition, grain size, texture, porosity, and strength.

Rock (music)

Rock music refers to a large family of popular musical styles that emerged in the mid-20th century. Early forms grew out of a mix of blues, rhythm and blues, country, and other vernacular traditions, and they were shaped by amplified instruments—especially the electric guitar—and a strong backbeat.

Over time rock developed a wide range of subgenres and regional scenes. Some broad categories include:

  • Early rock and roll — the initial, dance-oriented styles of the 1950s.
  • Hard rock and heavy rock — styles that emphasize louder, more aggressive electric guitar and rhythm sections.
  • Punk and alternative rock — movements that often favor simplicity, directness, or experimentation over mainstream conventions.
  • Progressive rock and art rock — strains that incorporate complex arrangements, extended compositions, and influences from classical or jazz traditions.

Rock has influenced fashions, technologies (such as amplification and recording), and youth cultures worldwide. Performances range from intimate club shows to large stadium concerts, and the genre has continued to evolve by integrating elements from electronic music, hip-hop, folk, and international styles.

Other common senses

  • As a material object, a rock can simply mean a single stone or boulder—an individual piece of naturally occurring mineral matter.
  • In food, rock candy describes large sugar crystals formed by crystallization on a string or stick.
  • As a verb, to “rock” means to move back and forth or from side to side, and it appears in contexts such as rocking a cradle or a chair.
  • Figuratively, to say something “rocks” or someone “rocks” is informal slang meaning that it is excellent or impressive.

Practical uses and cultural presence

Rocks and stones have a long history of use in tools, building materials, monuments, and art. Geologists, architects, archaeologists, and engineers study and apply knowledge of rocks in many fields. Meanwhile, rock music as a cultural form continues to be a major presence in media, live entertainment, and social movements, adapting to new technologies and tastes.

  • Minerals and mineralogy
  • Plate tectonics and the rock cycle
  • History and subgenres of rock music
  • Crystallization and sugar confectionery (rock candy)