Pendulum

[pen-juh-luh m, pen-duh-] /ˈpɛn dʒə ləm, ˈpɛn də-/

noun
1.
a body so suspended from a fixed point as to move to and fro by the action of gravity and acquired momentum.
2.
Horology. a swinging lever, weighted at the lower end, for regulating the speed of a clock mechanism.
3.
something that tends to move from one position, condition, etc., to the opposite extreme and then back again:
In a democratic society, the pendulum of political thought swings left and right.
/ˈpɛndjʊləm/
noun
1.
a body mounted so that it can swing freely under the influence of gravity. It is either a bob hung on a light thread (simple pendulum) or a more complex structure (compound pendulum)
2.
such a device used to regulate a clockwork mechanism
3.
something that changes its position, attitude, etc fairly regularly: the pendulum of public opinion
n.

1660, from Modern Latin pendulum (1643), noun use of neuter of Latin adjective pendulus “hanging down,” from pendere “to hang” (see pendant). The Modern Latin word is perhaps a Latinization of Italian pendolo.
pendulum
(pěn’jə-ləm)
A mass hung from a fixed support so that it is able to swing freely under the influence of gravity. Since the motion of pendulums is regular and periodic, they are often used to regulate the action of various devices, especially clocks.