1. Coming next after the twentieth in position
   - twenty-first

See also: ordinal

Encyclopedia: 21st

• bacillus
• Bacillus anthracis
• Bacillus globigii
• Bacillus subtilis
• bacitracin
• back
• back and forth
• back away
• back bacon
• back boiler
• back brace
• back breaker
• back burner
• back channel
• back circle
• back country
• back end
• back entrance
• back exercise
• back judge
• back matter
• back of beyond
• back of Bourke
• back off
• back out