1. Not arranged in order
   - disordered 
2. Not arranged in order hierarchically
   - ungraded, unranked

See also: nonhierarchic, nonhierarchical

• genus Smiledon
• genus Smyrnium
• genus Sobralia
• genus Solandra
• genus Solanopteris
• genus Solanum
• genus Solea
• genus Soleirolia
• genus Solenopsis
• genus Solenostemon
• genus Solidago
• genus Somateria
• genus Sonchus
• genus Sonora
• genus Sophora
• genus Sorbus
• genus Sorex
• genus Sorghum
• genus Spadella
• genus Spalax
• genus Sparaxis
• genus Sparganium
• genus Sparmannia
• genus Spartina
• genus Spartium