1. Having no curves
   - uncurved

See also: straight

• substituent
• substitutability
• substitutable
• substitute
• substitute teacher
• substituting
• substitution
• substitution class
• substitutional
• substitutionary
• substitutive
• substract
• substrate
• substratum
• substring
• substructure
• subsume
• subsumption
• subsurface
• subsystem
• subtenant
• subtend
• subterfuge
• subterminal
• subterranean