1. A short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead
   - protactinium, protoactinium, Pa

Type of: metal, metallic element

• genus Stizostedion
• genus Stokesia
• genus Storeria
• genus Strekelia
• genus Strelitzia
• genus Strepera
• genus Strepsiceros
• genus Streptocarpus
• genus Streptococcus
• genus Streptomyces
• genus Streptopelia
• genus Streptosolen
• genus Strix
• genus Strobilomyces
• genus Strombus
• genus Strongylodon
• genus Strophanthus
• genus Stropharia
• genus Struthio
• genus Struthiomimus
• genus Strymon
• genus Sturnella
• genus Sturnus
• genus Stylomecon
• genus Stylophorum