Other forms: pendula, pendulums
A pendulum is a hanging weight that swings steadily. A pendulum clock, the pendulum swings, swing like a pendulum.
Its period depends on its length and almost nothing else, which is what made pendulum clocks the most accurate timekeepers for nearly three hundred years. Galileo noticed the property and Huygens built the clock. Figuratively, the pendulum swings back describes opinion or politics reversing, and it is one of the most-used metaphors in commentary. Note Foucault's pendulum, which demonstrates the earth's rotation.
1nounpendulumA hanging weight that swings steadily.
“The pendulum is about a metre long and swings once a second.”
2nounpatternA pattern of opinion swinging back and forth.
“In fashion, the pendulum has swung back from tight jeans to loose ones.”
pendulum is a swinging weight.
Latin pendulus means hanging, from pendere, to hang. Pending, depend, suspend and pendant come from the same hanging.
Latin
pendulus — hanging
English, today
pendulum
Borrowed from the neuter of Latin pendulus (“hanging”).
Etymology from Wiktionary, CC BY-SA