"No, it's just business. And business is business.""
Business was the activity of creating income by producing, or buying and selling goods and services. It was, as well, the place where this activity occurred. One who conducted business was known as a businessman.
Ferengi education employed a work-study approach that included apprenticeships in a wide range of business and economic fields. (DS9: "A Man Alone")
In 2254, Captain Christopher Pike imagined a life, if he did resign from Starfleet, where he entered into business on Regulus or the Orion colony. (TOS: "The Cage", "The Menagerie, Part I")
Shortly after the establishment of Deep Space 9 and the discovery of the Bajoran wormhole in 2369, Odo observed that "Business is good, Quark. You're almost making an honest living." (DS9: "A Man Alone")
According to Quark, that was an "old Ferengi expression. Usually when we say that someone has the lobes, we mean that they have a keen business sense." (DS9: "Starship Down")