World War I is not a proper noun. Proper nouns are specific names given to particular people, places, organizations, or events. They are capitalized to distinguish them from common nouns. However, the term “world war” is a common noun because it refers to a general type of conflict that involves multiple nations on a global scale.
In the case of World War I, it is a specific war that occurred between 1914 and 1918, involving many countries around the world. The term “World War I” is capitalized because it is a proper noun referring to a particular historical event. It is important to note that “World War I” is the official name given to this conflict, and the use of Roman numerals (I) is common to differentiate it from subsequent world wars.
When referring to World War I in a more general sense, without attaching the full title, it is acceptable to leave the word “war” uncapitalized. For example, you could say “the war” or “the First World War” without capitalizing the word “war.”
It’s worth mentioning that the same rules apply to other wars as well. For instance, World War II is a proper noun, and when you refer to it specifically, you capitalize the entire term. However, when referring to it more generally, you can leave “war” uncapitalized.
While World War I is a proper noun, the term “world war” is a common noun. The capitalization depends on whether you are using the full title or referring to it in a more general sense.