X_3 is a term that can refer to various concepts depending on the context. In mathematics, it often denotes a specific variable or function within a larger equation or system. In technology, X_3 might represent a version of software or a model of a device, indicating its place in a series of updates or iterations. In the realm of gaming, X_3 could refer to a specific title or version of a game, such as X3: Reunion, which is part of the X series of space simulation games. This series is known for its complex economic systems and open-world gameplay, allowing players to explore and trade in a vast universe.