1. One billionth 10^(-9); more generally, very small

Encyclopedia: Nano-

• Usonian
• USP
• USPS
• usquebaugh
• USS
• USS Cole
• Ussher
• USSR
• USSS
• Ustilaginaceae
• Ustilaginales
• Ustilaginoidea
• Ustilaginoidea virens
• Ustilago
• Ustilago maydis
• Ustinov
• usual
• usually
• usualness
• usufruct
• usufructuary
• Usuli
• Usumbura
• usurer
• usurious