firma

Here is the trap. Firma is the adjective, meaning steady or solid; a business firm is firmao, a separate root with an extra syllable. They look near enough identical that English speakers merge them, and then write about a solid company when they meant a company at all. Otherwise firma behaves as you would expect and stretches to abstractions happily: a firma decido, a firma promeso, a firma amikeco. Firmigi means to make something firm, and firmeco names the quality itself.