(physics) The mechanics of objects moving at velocities comparable to the speed of light; is compatible with the special and general theories of relativity.

(physics) The study of the motion of individual particles.

The science that studies the mechanical behaviour of rock.

(physics, mathematics) The mathematical basis for quantum mechanics in which light and subatomic particles have the characteristics of both waves and particles.

(mechanics) The branch of mechanics dealing with gases and liquids, either at rest or in motion.

The application of mechanics (especially fluid mechanics) to soils, especially as a basis for the design and construction of building foundations and earthworks.

(astronomy) The dynamics of celestial bodies subject to mutual gravitational attraction.

(archaic) In the 19th century, engineering and other mechanical fields of expertise (comparable to performing arts and the fine arts).

Any mechanical (or other) system used to keep one or more variable parameters constant, or within specified bounds.

plural of mechanical pencil