WordNet records no synonym and no antonym for partnership. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the members of a business venture created by contract
a cooperative relationship between people or groups who agree to share responsibility for achieving some specific goal
“effective language learning is a partnership between school, teacher and student”
Synonyms, antonyms and the broader and narrower relations for partnership come from Princeton University’s WordNet. Full sources and licences.
a contract between two or more persons who agree to pool talent and money and share profits or losses