Which word describes something that tends to induce sleep?

The word "soporific" specifically refers to something that is able to induce sleep or has a calming effect that leads to drowsiness. It derives from the Latin word "sopor," meaning "deep sleep." Generally, soporifics can refer to medications, environments, or even literary styles that have a serene, sleep-inducing quality. The other choices do not carry this meaning.

"Quiescent" refers to a state of inactivity or dormancy, which does not explicitly imply inducing sleep but rather a lack of movement or an unchanging state. "Querulous" describes a tendency to complain or show a whiny attitude, while "reticent" means being reserved or not revealing one's thoughts easily. None of these words relate to the act of inducing sleep, making "soporific" the clear choice.