Definitions:

1. a component that is added to something to improve it noun
   • the addition of a bathroom was a major improvement
2. a quantity that is added noun
   • there was an addition to property taxes this year
3. the act of adding one thing to another noun
   • the addition of flowers created a pleasing effect

Synonyms:

• accession
• add-on
• improver
• increase
• plus
• summation

NearBy Words:

• additional
• additionally