somniferous

(-nĭf'ĭk)
adj.
Inducing sleep; soporific.

somniferously som·nif'er·ous·ly adv.

(som-NIF-ik)

adjective
Causing sleep.

Etymology
From Latin somnificus (causing sleep), from somnus (sleep) + facere (to make). Ultimately from Indo-European root swep- (to sleep) that is also the source of insomnia, hypnosis, soporific (inducing sleep) and somnambulate (to walk in sleep)

Usage
"Each week in Horse & Hound, the showjumper's bible, advertisements for 'natural sedatives' with somnific names - Placid, So-Kalm, Tranquillity - promise to 'soothe away your horse's competition nerves and prevent nervousness and excitability without impairing performance'." — Richard McClure; Skulduggery at the Stables; The Independent (London, UK); Aug 30, 1999.

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adjective

Inducing sleep or sedation: hypnotic, narcotic, opiate, sedative, sleepy, slumberous, somnifacient, somnific, somnolent, soporific. See awareness/unawareness.

(somnif′ərus)
adj

Inducing or causing sleep.

Producing sleep.