Following his earlier post about a Relationships Thesaurus, PG was intrigued while considering the enormous number of various types of relationships and shades of relationships between people (and groups of people) as compared with the more limited scope of relationships he sees in many books and stories.
Here a single sub-part under Relationships from WordHippo that PG picked because most of the synonyms had little or nothing to do with romantic or family relationships.
Noun
The state of cooperating, being allied or working together:
cooperation
partnership
union
communications
confederation
rapport
collaboration
conjunction
alliance
hookup
linkup
association
liaison
affiliation
connection
tie-up
coalition
relation
compact
federation
trust
axis
league
cartel
coterie
clique
copartnership
society
brotherhood
club
combination
fraternity
sisterhood
sorority
co-partnership
joint venture
strategic partnership
contractual cooperation
strategic relationship
strategic alliance
mutually beneficial alliance
mutually beneficial relationship
cross-holding
mutually beneficial
partnership
equity alliance
confederacy
guild
combine
consortium
group
syndicate
organization
block
order
bloc
congress
sodality
organisation
labour union
workers’ association
labor union
trade union
Bund
companionship
consociation
faction
link
ring
party
fellowship
mob
friendship
togetherness
body
gang
community
participation
enterprise
crew
chumminess
cahoots
bargain
arrangement
contract
deal
link-up
protocol
understanding
settlement
covenant
entente
accord
bond
accommodation
coordination
hook-up
tie-in
business arrangement