auxiliary auxiliary /ɑːgˈzɪliːɛri/

adjective

1. () Functioning in a supporting capacity  ( subsidiary , auxiliary , supplemental , supplementary )
   functioning in a supporting capacity
    The main library and its auxiliary branches
   the main library and its auxiliary branches
   
2. Furnishing added support  ( accessory , adjunct , adjuvant , ancillary , appurtenant , auxiliary )
   furnishing added support
    An ancillary pump
   an ancillary pump
    An adjuvant discipline to forms of mysticism
   an adjuvant discipline to forms of mysticism
    The mind and emotions are auxiliary to each other
   The mind and emotions are auxiliary to each other
   

noun

1. () Someone who acts as assistant  ( aide , auxiliary )
   someone who acts as assistant