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Synonyms for Assistant (same or very similar meaning)

WordNet sense 1 (a person who contributes to the fulfillment of a need or furtherance of an effort or purpose):
help, helper, supporter

WordNet sense 2 (of or relating to a person who is subordinate to another):

WordNet sense 3 (lower in rank or importance):
low-level, subordinate

From the ODE community, based on WordNetadd/edit