adjuvant

noun

: one that helps or facilitates: such as

a

: an ingredient (as in a prescription or a solution) that modifies the action of the principal ingredient

b

: something (such as a drug or method) that enhances the effectiveness of medical treatment

used chemotherapy as an adjuvant to surgery

c

: a substance (such as one added to a vaccine) enhancing the immune response to an antigen

Did you know?

Things that are adjuvant rarely get top billing—they're the supporting players, not the stars. But that doesn't mean they're not important. An adjuvant medicine, for example, can have a powerful healing effect when teamed up with another medicine or curative treatment. Adjuvant descends from the Latin verb adjuvare ("to aid"), which also gave English the nouns coadjutor ("assistant") and aid. These days, adjuvant tends to turn up most often in medical contexts, but it can also be used in the general sense of "serving to aid." Likewise, the noun adjuvant can mean "a drug or method that enhances the effectiveness of medical treatment" or simply "one that helps or facilitates."

Examples of adjuvant in a Sentence

Recent Examples on the Web

But these vaccines sometimes require additional compounds called adjuvants or other strategies that have been shown to safely boost the immune system’s response to the vaccine. —Meghan Bartels, Scientific American, 27 Mar. 2026

Sinclair’s work on senescence intersects with new therapeutic directions in oncology, from CAR-T failures linked to T-cell exhaustion to the growing interest in senolytic adjuvants. —Gilberto Lopes, STAT, 12 Feb. 2026

Despite broad evidence that using such adjuvants are safe, Kennedy has argued that aluminum in vaccines is linked to allergies and other health problems. —Jen Christensen, CNN Money, 6 Jan. 2026

The panel also heard a presentation from ACIP member Evelyn Griffin on aluminum adjuvants in vaccines. —Joseph Choi, The Hill, 5 Dec. 2025

Word History

Etymology

borrowed from Medieval Latin adjuvant-, adjuvans, going back to Latin, present participle of adjuvāre "to help, aid, facilitate" — more at aid entry 1

First Known Use

1583, in the meaning defined above

Rhymes for adjuvant

• movant
• neoadjuvant

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Medical Definition

adjuvant

1 of 2 adjective

ad·​ju·​vant ˈaj-ə-vənt 

1

: serving to aid or contribute

2

: assisting in the prevention, amelioration, or cure of disease

adjuvant chemotherapy following surgery

adjuvant

2 of 2 noun

: one that helps or facilitates: as

a

: an ingredient (as in a prescription or solution) that facilitates or modifies the action of the principal ingredient

the beneficial activity of the spray is enhanced by adjuvants

b

: something (as a drug or method) that enhances the effectiveness of a medical treatment

used chemotherapy as an adjuvant to surgery

c

: a substance enhancing the immune response to an antigen