Soporific is a synonym for soporous. The term is derived from the Latin word "sopor", which means "sleep." It is used to describe anything that induces sleep or causes a person to feel drowsy. Another synonym for soporous is hypnotic, which is often used to refer to drugs that cause drowsiness. Sedative is also a synonym and is used to describe any drug or substance that causes relaxation and sleepiness. Other synonyms for soporous include tranquillizing, somnolent, and heavy. These words can all be used to describe anything that causes a person to feel drowsy or sleepy.