hi! this is a pretty popular question in this sub, so check out some previous answers here:

• this is /u/elos_'s pet question :) S/he gives it the treatment in Why is WW1 considered the first world war?, and has more to say in First real world war and Why didn't/don't historians refer to the Seven Year War as the first world war?

• here's an older post with several respondents The Seven Year's War had a theater in every continent and involved all of the major powers at the time -- why don't we refer to it as World War I?

These posts have been archived, so if you have follow-up questions, ask them here & mention the relevant user's username so they'll be notified