What is a partnership or joint venture?

"A joint venture is 'an undertaking by two or more persons jointly to carry out a single business enterprise for profit. [Citations.]'... 'Like partners, joint venturers are fiduciaries with a duty of disclosure and liability to account for profits.'" (Weiner v. Fleischman (1991) 54 Cal.3d 476, 482.) Both a partnership and a joint venture may be formed orally or "'assumed to have been organized from a reasonable deduction from the acts and declarations of the parties.'" (Id. at pp. 482-483.)