Here's why:
* It names a specific being: It refers to a deity, a supreme being, often associated with specific religions.
* It acts as the subject or object of a sentence: For example, "God created the world." (subject) or "We pray to God." (object)
However, it's worth noting that "God" can sometimes function as an interjection when used in expressions like:
* "Oh, God!" (expressing surprise or dismay)
Ultimately, the specific part of speech depends on how the word is used in a given sentence.