Somnifacient is a term used to refer to any substance that can cause drowsiness or sleepiness. Synonyms for this word include sedative, hypnotic, soporific, narcotic, tranquilizer, and sleeping pill. These terms describe medications and substances that can be used to induce sleep or reduce anxiety symptoms. For example, sedatives are often prescribed to patients who suffer from insomnia, while tranquilizers are often used to calm an agitated or anxious individual. Soporifics can be used to relieve pain and induce sleep, while hypnotics are used to treat sleep disorders and help individuals fall asleep more quickly. Narcotics are also used as pain relievers and can cause drowsiness as a side effect.