supplemental

supplemental — adjective

1. Added to something else in order to make it fuller, more effective, or sufficien

1.adjectiveB2
Definition

Added to something else in order to make it fuller, more effective, or sufficient — for example, a supplemental income that helps cover household expenses, or a supplemental reading list that gives extra background on a topic.

Example

Ava took a supplemental weekend job to save money for her trip to Japan.

supplemental + noun (job) for extra earnings

The professor gave students a supplemental reading packet on the topic.

attributive use: supplemental reading packet

Common collocations
  • supplemental income
  • supplemental insurance
  • supplemental funding
  • supplemental reading
  • supplemental materials
  • supplemental vitamin
  • supplemental dose
  • supplemental water
  • supplemental budget
Synonyms
  • additional

    Most common and neutral; works in any context where 'supplemental' is used

  • extra

    Informal and very common in everyday speech; implies 'more than usual'

  • supplementary

    Interchangeable with 'supplemental' in most contexts, slightly more common in British English

  • auxiliary

    Emphasizes a supporting or backup role; more technical (e.g., auxiliary power)

Antonyms
  • primary

    The main or most important item, to which supplemental items are added

  • essential

    Something that is necessary rather than extra or optional

Grammar Patterns

supplemental + noun

be supplemental to + noun

Usage Note

Typically used before a noun (e.g., supplemental income, supplemental insurance). More common in formal writing and professional contexts than in everyday conversation, where 'extra' or 'additional' is preferred. For example, native speakers say 'extra cash' rather than 'supplemental cash'.

Common Mistakes

I need some supplemental money for the bus fare.
I need some extra money for the bus fare.
'Supplemental' sounds too formal for everyday, small-scale needs; use 'extra' or 'additional' instead.
She bought a supplemental dress for the party.
She bought an extra dress for the party.
'Supplemental' suggests filling a lack or completing a system, not simply buying another of something.

Word family

Synonym discussion

Sense: adjective/1

All four words describe something added to what is already present, but they differ in register and emphasis. 'Additional' is the most neutral and widely used — it simply means 'more on top of what exists' (e.g., 'We need additional staff for the event'). 'Extra' is the informal everyday equivalent, used for anything beyond the usual amount (e.g., 'I packed an extra pair of socks'). 'Supplemental' and 'supplementary' are nearly identical and more formal; they often imply that the addition fills a gap or completes something that was incomplete ('supplemental insurance fills gaps in basic coverage'). 'Auxiliary' emphasizes a supporting or backup function and is more technical, often used for equipment or systems ('auxiliary power supply'). In short: use 'extra' for casual speech, 'additional' for neutral writing, and 'supplemental'/'supplementary' when the addition makes something more complete.

supplementary ↗additional ↗extra ↗auxiliary ↗

Common collocations

Nouns

Phrases

  • as a supplement to

Prepositions

Etymology

LatinOld FrenchEnglish

Derived from the Latin verb 'supplere' (to fill up, complete), formed from 'sub-' (from below, up from under) and 'plere' (to fill). The noun 'supplement' entered English through Old French in the 14th century, and the adjective 'supplemental' emerged later, around the 17th century, to describe something that serves as an addition to make something whole or sufficient.