What part of speech is the word earth?

The word "earth" can be several parts of speech depending on how it's used in a sentence:

* Noun: When referring to the planet we live on.

* Example: "The Earth is a sphere."

* Noun: When referring to soil or dirt.

* Example: "He dug in the earth to plant the seeds."

* Adjective: When describing something as being made of earth or soil.

* Example: "They built an earth oven."

So, without context, it's impossible to say definitively what part of speech "earth" is.