Changeable means able to be altered or modified, or describes something that shifts frequently and unpredictably. When your teacher says the schedule is changeable, she means it might need adjusting based on what happens during the day.

The word often describes things that vary without warning. Changeable weather might bring sunshine in the morning and thunderstorms by afternoon. A person with a changeable mood might be laughing one minute and irritable the next, making them hard to predict. These frequent shifts can make planning difficult: if your friend has changeable opinions about what game to play, you might spend more time deciding than actually playing.

Some things are changeable by design, which can be useful. A changeable display in a store can be updated for different seasons. Software with changeable settings lets you customize how it works. In these cases, being changeable is an advantage because it means being adaptable and flexible.

The word carries different feelings depending on context. Calling weather changeable is just descriptive, but calling someone's promises changeable suggests they can't be trusted. When someone is changeable in their commitments, they keep switching their plans, which can frustrate people counting on them.