It’s Uncle Marvin’s unpredictability that makes family functions so interesting — you just never know what he’s going to do! Unpredictability is the trait of doing things in a way that is irregular and cannot be predicted.
Unpredictability contains the word predictability, which describes the quality of doing things in a regular way, time after time. Unpredictability is the opposite of predictability. Because Uncle Marvin is so marked by unpredictability, you never bring your friends to family parties, fearing that Uncle Marvin might do something wacky at any moment. Unpredictability can be exciting, but it can also be scary or unpleasant never knowing what someone is going to do next.