1. (noun) a component that is added to something to improve it

• addition
• improver

2. (noun) a supplementary component that improves capability

• accessory
• appurtenance
• supplement

1. (noun) a component that is added to something to improve it

• additive
• afterthought
• annex
• annexe
• extension
• wing
• attachment
• elongation
• extension

2. (noun) a supplementary component that improves capability

• auto accessory
• computer accessory
• fitting
• fixings
• trimmings

1. (noun) a component that is added to something to improve it

• component
• constituent
• element

2. (noun) a supplementary component that improves capability

• component
• constituent
• element

1. (noun) a component that is added to something to improve it

• add
• bestow
• bring
• contribute
• impart
• lend
• add on
• ameliorate
• amend
• better
• improve
• meliorate

2. (noun) a supplementary component that improves capability

• accessorial
• accessory
• accessory
• adjunct
• adjunct
• adjuvant
• adjuvant
• ancillary
• ancillary
• appurtenant
• appurtenant
• auxiliary
• auxiliary
• add on
• affix
• append
• supplement
• appertain
• pertain
• auxiliary
• auxiliary
• subsidiary
• subsidiary
• supplemental
• supplemental
• supplementary
• supplementary
• supplement