auxiliary
1. [ noun ] (work) someone who acts as assistant
Synonyms: aide
Related terms: assistant nursing_aide
2. [ adjective ] functioning in a subsidiary or supporting capacity
Synonyms: supplemental supplementary subsidiary
Examples:

"the main library and its auxiliary branches"

Related terms: secondary
3. [ adjective ] relating to something that is added but is not essential
Synonyms: adjunct ancillary adjuvant appurtenant subsidiary accessory
Examples:

"an ancillary pump" "an adjuvant discipline to forms of mysticism" "The mind and emotions are auxilliary to each other"

Related terms: supportive