Which software term refers to enhancements that significantly improve features?

The term that refers to enhancements that significantly improve features is upgrades. Upgrades are typically major versions or releases of software that not only include bug fixes but also introduce substantial new features, functionality, or improvements to the existing capabilities of a program. This contrast often makes upgrades distinguishable from other enhancements, such as updates, which may merely refine or fix existing features without substantial changes, or plug-ins, which are additional components that add specific features to an existing program but do not represent a complete overhaul or significant improvement of the software itself. Compatibility refers to the ability of software to work with other software or systems, and while it is important, it does not relate to improvements in features.