“Partner” refers to a person who is associated with another in some activity or enterprise. Some synonyms for “partner” are “ally”, “associate”, and “collaborator”.
“Ally” suggests a person or group that is joined with another for a common purpose, often in a supportive or cooperative way. For example, “In business, it’s important to have reliable allies.” This shows that an ally is similar to a partner in that they work together towards a shared goal.
“Associate” implies a person with whom one is connected in a business, professional, or social context. “He is an associate at the law firm.” Here, “associate” indicates a relationship that is similar to that of a partner, although perhaps not as closely tied.
“Collaborator” refers to someone who works jointly with others on a project or task. “The scientists were collaborators on the research study.” This highlights the cooperative nature of a collaborator, which is also a characteristic of a partner.