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A sandbox game is a video game with a gameplay element that provides players a great degree of creativity to interact with, usually without any predetermined goal, or alternatively with a goal that the players set for themselves. Such games may lack any objective, and are sometimes referred to as non-games or software toys. More often, sandbox games result from these creative elements being incorporated into other genres and allowing for emergent gameplay. Sandbox games are often associated with an open world concept which gives the players freedom of movement and progression in the game's world. The term "sandbox" derives from the nature of a sandbox that lets people create nearly anything they want within it.
Some games offer a separate sandbox mode, where the player can use a game's creative systems with fewer constraints.
From wikipedia which I understand this is the accepted baseline definition of a sandbox game.
Creative Mode in 7 Days to Die is the true sandbox for it, as it has been stated many times. So if a player wants to a true sandbox mode for the game, they need to turn on the creative menu.