1. Sleep inducing
   - soporific, somniferous, somnific, hypnogogic, hypnagogic 
2. Inducing mental lethargy
   - narcotic, soporific

See also: depressant, uninteresting

• sustainable
• sustained
• sustained yield
• sustainer
• sustaining pedal
• sustaining program
• sustainment
• sustenance
• sustentacular
• sustentation
• sustentative
• susurrant
• susurrate
• susurration
• susurrous
• susurrus
• Sutherland
• sutler
• sutra
• suttee
• sutura
• sutura coronalis
• sutura frontalis
• sutura intermaxillaris
• sutura internasalis