An apartment is a housing unit that shares a building with other similar units. They are usually smaller than houses.
811 East 68th Street
James Kirk's apartment
Admiral James T. Kirk owned in an apartment in San Francisco in 2285. It was in a tall skyscraper in San Francisco and featured sweeping views of the city, the bay, Alcatraz, the Golden Gate Bridge and at least two other prominent 23rd century skyscrapers. The apartment featured a fireplace in the living room with a curved wall and mosaic treatment behind it. To the left of the fireplace and to the right of the windows there was a metallic sculpture that perhaps could have been a model of the skyscraper the apartment was in. Kirk filled the apartment with antiques, reflecting his fondness for them; in particular, a lot of the antiques were of a nautical nature. Also among the items were 18th and 19th century Earth firearms and a late 20th century Earth computer. (Star Trek II: The Wrath of Khan; Star Trek III: The Search for Spock)
Reginald Barclay's apartment
Lieutenant Reginald Barclay moved into a new apartment in San Francisco in 2374, after joining the Pathfinder Project. He still had not unpacked all of his belongings when he was visited by Deanna Troi in 2376. (VOY: "Pathfinder")
Kathryn Janeway's apartment
In an alternate timeline in which the USS Voyager returned to Earth in 2394, Admiral Kathryn Janeway lived in a San Francisco apartment with a view of the Golden Gate Bridge. In 2404, she hosted the ten year anniversary party for the event there. (VOY: "Endgame")
The backdrop view of San Francisco from Kirk's apartment was previously used in the movie The Towering Inferno (1974). The backdrop in that movie was used for a 135th floor restaurant overlooking San Francisco. The metallic sculpture in Kirk's apartment near the fireplace bears a striking resemblance to the "Glass Tower" skyscraper in the movie.