Why is the first world war called "the first world war"?Explain with reason.
To answer this, you have to look at both parts of the name.
First, this was a world war because it involved countries in practically every part of the world. European countries were most strongly involved, but there were American countries, Asian countries, and even countries such as Australia and New Zealand. African countries were affected because their colonizers took many of their men to work or fight in the war. In this sense, it was a world war.
In addition, this was the first of the two world wars. That's why it is called the "First" World War. Please note that this name was not applied to it until the Second World War came around. Before that, it was known as the Great War.