auxiliary

American  

[awg-zil-yuh-ree, -zil-uh-] / ɔgˈzɪl jə ri, -ˈzɪl ə- /

adjective

1. additional; supplementary; reserve.

   an auxiliary police force.

2. used as a substitute or reserve in case of need.

   The hospital has an auxiliary power system in case of a blackout.

   Synonyms:

   secondary, ancillary, backup

3. (of a boat) having an engine that can be used to supplement the sails.

   an auxiliary yawl.

4. giving support; serving as an aid; helpful.

   The mind and emotions are auxiliary to each other. Passion is auxiliary to art.

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noun

auxiliaries plural

1. a person or thing that gives aid of any kind; helper.

   Synonyms:

   help, assistant, ally, aide

2. an organization allied with, but subsidiary to, a main body of restricted membership, especially one composed of members' relatives.

   The men's club and the ladies' auxiliary were merged into one organization.

3. auxiliary verb.

4. auxiliaries, foreign troops in the service of a nation at war.

5. Navy. a naval vessel designed for other than combat purposes, as a tug, supply ship, or transport.

6. Nautical. a sailing vessel carrying an auxiliary propulsion engine or engines.

auxiliary British  

/ -ˈzɪlə-, ɔːɡˈzɪljərɪ /

adjective

1. secondary or supplementary

2. supporting

3. nautical (of a sailing vessel) having an engine

   an auxiliary sloop

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noun

1. a person or thing that supports or supplements; subordinate or assistant

2. nautical

   1. a sailing vessel with an engine

   2. the engine of such a vessel

3. navy a vessel such as a tug, hospital ship, etc, not used for combat

Other Word Forms

Noun Inflected Forms

• auxiliaries
  plural

Etymology

Origin of auxiliary

1595–1605; < Latin auxiliārius assisting, aiding, helping, equivalent to auxili ( um ) aid, help ( aux ( us ) increased, augmented (past participle of augēre: aug- increase + -sus, variant of -tus past participle suffix) + -ilium noun suffix) + -ārius -ary

Explanation

When you're offering something in support of an already existing thing, you're offering something auxiliary. The auxiliary police will help out the regular police with things like directing traffic and crowd control when there's a special event in town. The Latin word auxilium means "help," and so auxiliary means something that "helps" by providing backup or support. Think of auxiliary verbs (sometimes called helper verbs), that provide support within a verb phrase, as "is" does in "Helen is playing." You can have an auxiliary engine in a car, an auxiliary cook at a restaurant, an auxiliary electrical network at a factory, or auxiliary troops standing by during battle. A "Ladies Auxiliary" functions as support for institutions such as churches, synagogues, or charities.

Example Sentences

Using auxiliary degrees of freedom is not a new concept in physics.

From Science Daily • Jun. 16, 2026

The “blue boat,” survivors said, eventually took on board all 16 crew members, who had managed to clamber into a pair of auxiliary skiffs attached to the Negra Francisca.

From Los Angeles Times • Jun. 15, 2026

First up is Honeywell Aerospace, which makes auxiliary power units for planes and engines for military equipment as well as electronics and software for aircraft.

From Barron's • Jun. 2, 2026

He added that France's partners would also share in the development of "auxiliary" capacities under the new nuclear doctrine: space-based alarm systems; air defence to shoot down incoming drones and missiles; and long-range missiles.

From BBC • Mar. 2, 2026

Just then the three members of the defunct ladies’ auxiliary, Frieda, Betty, and Liz, stomped into the crowd surrounding Ignatius.

From "A Confederacy of Dunces" by John Kennedy Toole

Related Words

• ancillary