How can volcanoes be classified on the basis of their activity?

On the basis of their activity, volcanoes can be classified into three types:

1. Active volcanoes — They constantly eject lava, gases and ash. For example- Sabancaya in Peru.
2. Dormant volcanoes — They remain dormant but can suddenly erupt and again go dormant. For example- The Vesuvius volcano in Italy.
3. Extinct volcanoes — They are volcanoes where there has been no volcanic activity since long. Their crater usually developes into a lake. For example- For example- Arthur's seat at Edinburgh in Scotland.