soporific
adjective
[ ˌsɒpəˈrɪfɪk ]
• tending to induce drowsiness or sleep.
• "the motion of the train had a somewhat soporific effect"
soporific
noun
• a drug or other substance that induces drowsiness or sleep.
Origin:
mid 17th century: from Latin sopor ‘sleep’ + -fic.
