General usage:
* Planet: This is the most straightforward option when referring to our planet in an astronomical context.
* World: This is a more poetic or philosophical term, often implying the whole of humanity and its experiences.
* Globe: This emphasizes the spherical shape of Earth.
Specific contexts:
* Soil: When referring to the ground we walk on.
* Ground: This is another option for the surface of the earth.
* Land: When contrasting it with water or the sky.
Other options:
* Terra: This is a Latin word meaning "earth" and can be used in more formal or scientific settings.
* Gaia: This is a Greek goddess who personifies the Earth.
Ultimately, the best common noun for "earth" depends on what you want to emphasize and the specific situation.