KWER-uh-luhs
(adjective) Complaining in a petulant or whining manner.
His querulous tone made it clear he wasn’t happy with the service.
Fun Fact
“Querulous” comes from the Latin queri, meaning “to complain.” It describes not just dissatisfaction, but persistent, nitpicky, or whiny complaining. It’s a favorite word in literature to portray cranky characters—from Dickensian debtors to sitcom neighbors.
UN-juh-layt
(verb) To move with a smooth, wave-like motion; to have a wavy form, surface, or appearance.
The tall grass undulated across the hillside in the breeze, rippling like a slow green tide.
From Latin undulatus, meaning “wavy,” derived from undula, a diminutive of unda, meaning “wave.” The Latin root unda is also the ancestor of words like abound, inundate, and redundant — all carrying the original sense of water flowing or overflowing. The word entered English in the early 17th century via scientific and descriptive writing.
Fun Fact
Undulation is one of nature’s most energy-efficient forms of locomotion. Snakes, eels, and even some bacteria move through undulation, using waves along their bodies to propel themselves forward with minimal energy loss. Engineers have studied this motion extensively in the development of soft robotics and underwater drones — some of the most advanced aquatic robots today mimic the undulating motion of rays and eels to navigate environments that rigid-hulled vessels simply cannot handle.