a feeling of sympathetic understanding
"She felt an instant sense of compatibility with her new mentor, as if they could read each other's minds without ever speaking a word."
capability of existing or performing in harmonious or congenial combination
"After months of dating, they finally realized their fundamental personality compatibility was strong enough to build a lasting life together."
The state of being compatible; in which two or more things are able to exist or work together in combination without problems or conflict.
"The new software update improved compatibility by allowing the program to run smoothly on older devices without crashing."
In plain English: Compatibility is when two things work well together without causing problems.
"The new software update improved compatibility with older devices."
Usage: Use compatibility to describe the ability of two or more items, systems, or people to coexist or function together without causing issues. It applies when you need to confirm that different parts fit well as a unit rather than clashing with one another.
The word compatibility comes from New Latin compatibilitas, which was formed by combining the root of compatible with a suffix meaning "state or condition." It entered English as a noun describing the quality of being able to exist together without conflict.