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1. A change for the better; progress in development
   - betterment, advance
    
2. The act of improving something
   "their improvements increased the value of the property"
    
3. A condition superior to an earlier condition
   "the new school represents a great improvement";
   - melioration

Derived forms: improvements

Type of: change of state, condition, shift, status, transformation, transmutation

Antonym: decline

Encyclopedia: Improvement