The difference between Accessory and Auxiliary

Accessory as an adjective:

Having a secondary, supplementary or subordinate function by accompanying as a subordinate; aiding in a secondary way; being additional; being connected as an incident or subordinate to a principal; contributing or being contributory. Said of people and things, and, when of people, usually in a bad sense

Accessory as an adjective (legal):

Assisting a crime without actually participating in committing the crime itself.

Accessory as an adjective:

Present in a minor amount, and not essential.

Accessory as a noun:

Something that belongs to part of another main thing; something additional and subordinate, an attachment.

Accessory as a noun (fashion):

An article that completes one's basic outfit, such as a scarf or gloves.

Accessory as a noun (legal):

A person who is not present at a crime, but contributes to it as an assistant or instigator.

Accessory as a noun (art):

Something in a work of art without being indispensably necessary, for example solely ornamental parts.

Auxiliary as an adjective:

Helping; giving assistance or support.

Auxiliary as an adjective:

Supplementary or subsidiary.

Auxiliary as an adjective:

Held in reserve for exceptional circumstances.

Auxiliary as an adjective (nautical):

Of a ship, having both sails and an engine.

Auxiliary as an adjective (grammar):

Relating to an auxiliary verb.

Auxiliary as a noun:

A person or group that acts in an auxiliary manner.

Auxiliary as a noun:

A sailing vessel equipped with an engine.

Auxiliary as a noun (grammar):

An auxiliary verb.

Auxiliary as a noun:

A marching band colorguard.