volcano is a noun that is used to refer to a mountain or hill typically conical in shape and composed of layers of solidified lava, tephra, and volcanic ash.
1. The volcano erupted last night.
2. Climbers were warned not to go near the volcano.
3. The hot lava spewed out of the volcano.
common mistakes include forgetting to capitalize the word when used to refer to a specific volcano, as in 'Mount St. Helens is an active volcano.'