1. Not required by rule or law
   - nonobligatory

See also: optional

• bug
• bug out
• bug-eyed
• bug-hunter
• bugaboo
• Buganda
• bugbane
• bugbear
• bugged
• bugger
• bugger all
• bugger off
• buggered
• buggery
• bugginess
• buggy
• buggy whip
• bugle
• bugle call
• bugler
• bugleweed
• bugloss
• bugologist
• bugology
• buhl