A pendulum can help reveal what is hidden to you with simple yes and no answers.
The word pendulum is a borrowing from Latin. The Latin word is not spelled differently. Pendulum entered Early Modern English circa 1660 CE. There are two plural versions of the word, pendula and pendulums.There are also two ways to pronounce pendulum: PEN-juh-luhm and PEN-dyuh-luhm. The d can either be pronounced like a j or a d. Both are widely accepted pronunciations.
Pendulums in practice are often a crystal hanging on a chain. A practitioner holds one end of the chain and dangles the crystal. The practitioner then asks a yes, no, or maybe style question. For yes, the pendulum will sway in one direction while it sways the other direction for no. Maybe or "ask again later" usually means no movement at all. Each pendulum has its own energy and practice, so make sure to familiarize yourself with your pendulum before assuming what the answers are. You can also use the pendulums with a pendulum board. These boards may be equipped with magnets to pull on the gravitation of the pendulum, and they can help a practitioner easily identify the response.
While many use pendulums in their craft, they are also used for other sciences. There are also scientific studies that suggest that pendulums are better for identifying your own thoughts and intentions over true divination.
Sources:
Olson, Jay A et al. “Ask the pendulum: personality predictors of ideomotor performance.” Neuroscience of consciousness vol. 2017,1 nix014. 2 Aug. 2017, doi:10.1093/nc/nix014
“Pendulum, N.” Oxford English Dictionary, Oxford UP, July 2023, https://doi.org/10.1093/OED/1162007246.
Personal experience.