union or fellowship arising from common responsibilities and interests, as between members of a group or between classes, peoples, etc.

to promote solidarity among union members.

community of feelings, purposes, etc.

community of responsibilities and interests.

noun

accord , agreement , alliance , comradeship , confederation , consensus , federation , fellowship , harmony , indivisibility , oneness , sameness , support , teamwork , unanimity , undividedness , unification , uniformity , union , cohesion , togetherness , unity