An inventory was a list of a business's material assets.
In 2370, Rom was completing the weekly stock inventory for Quark's. Quark came to pick up a misbehaving Nog from Deep Space 9's security office in his stead, explaining that he didn't want to interrupt his brother, as Rom was easily distracted and might lose count of the items he was inventorying. (DS9: "Sanctuary")
In 2371, Commander Benjamin Sisko ordered Nog to inventory the contents of Deep Space 9's Cargo Bay 12 despite them having just recently been inventoried as part of a test to help determine his seriousness about joining Starfleet. After Lieutenant Commander Jadzia Dax reported that he had inventoried the contents of the entire bay in under five hours, Sisko described his efforts as "impressive work." Dax noted that he had even found some things the station's crew had missed on the previous inventory. (DS9: "Heart of Stone")
In 2372, Quark, incredulous at Hanok's claims at the Karemma's honest business practices, questioned whether he had ever padded an inventory (claimed he had more items than he did). Hanok continued to deny he ever had. (DS9: "Starship Down")