predictable
Easy to guess because it happens the way you expect.
Predictable means you can tell what will happen before it actually happens. When something is predictable, it follows a pattern you recognize, so there are no real surprises.
A predictable movie might have a hero who always saves the day at the last minute, or a villain whose plans always fail in exactly the way you expected. After watching a few episodes of a TV show, the plots might become predictable: you can guess who will get in trouble, how they'll solve the problem, and what lesson they'll learn by the end.
People can be predictable too. If your friend always orders the same lunch, always picks the same seat, and always tells the same kind of jokes, their behavior is predictable. Sometimes this feels comfortable and reassuring. Other times it gets boring because you know exactly what's coming.
The word often carries a slightly negative feeling, especially about stories or entertainment. Calling a book predictable usually means it was disappointing because nothing unexpected happened. But in other contexts, predictable can be positive: a predictable bus schedule is reliable, and a predictable friend is someone you can count on.
The opposite of predictable is surprising, unexpected, or unpredictable.