1) Associate 2) Collaborator 3) Pardner 4) Partner 1) Auxiliary 2) Pardner 
• (n.) One who labors jointly with others to promote the same end.
(from the article `Opus Dei`) ...financially to Opus Dei, and demonstrate Christian virtue in their daily activities. Members serve a period of probation and attend monthly ...
Co·öp'er·a`tor noun [ Latin : confer French coopérateur .] One who labors jointly with others to promote the same end. ' Coöperators with the truth.' Boyle.