improvement

noun

1. an act of improving or the state of being improved.
2. a change or addition by which a thing is improved.
3. a person or thing that represents an advance on another in excellence or achievement: The new landlord is a great improvement over his greedy predecessor.
4. a bringing into a more valuable or desirable condition, as of land or real property; betterment.
5. something done or added to real property that increases its value.
6. profitable use, as of a period of time.

noun

1. the act of improving or the state of being improved
2. something that improves, esp an addition or alteration
3. alteration of the structure, fixtures, fittings, or decor of a building without changing its functionCompare conversion (def. 9)
4. (usually plural) Australian and NZ a building or other works on a piece of land, adding to its value