1. Plural of planetary: a gear or system of gears in which one gear revolves around another, used in transmissions and machinery.
Usage: technical; mechanical engineering
2. Plural of planetary: a type of nebula that appears round and glowing, resembling a planet when viewed through a telescope.
Usage: astronomy

Examples

• The transmission uses planetaries to transfer power efficiently from the engine to the wheels.
• Modern automatic transmissions rely on complex systems of planetaries to achieve multiple gear ratios.
• Astronomers discovered several beautiful planetaries in the constellation Lyra.
• The Ring Nebula is one of the most famous planetaries visible from Earth.
• Engineers designed the planetaries to minimize friction and heat loss in the gearbox.