sleep aid

Short definition from Wiktionary

Noun

1. 1
   Any drug, nutritional supplement, device, or behavioral method used to help a person to fall asleep, stay asleep, or have better sleep quality.
2. 2
   Any drug, nutritional supplement, device, or behavioral method used to help a person to fall asleep, stay asleep, or have better sleep quality: A pill (containing a drug or nutritional supplement) for this purpose.