Webster's dictionary defines "Continent" as one of the usually seven great divisions of land on the globe -- North America, South America, Europe, Asia, Africa, Australia and Antarctica.
Some consider Europe & Asia to be one continent -- That's where the qualifying "usually" comes from ie: Eurasia
Apparently some new cartographers are pushing the idea that the Middle East is another.
Islands don't count because...well, they're islands
Don't shoot the messenger, please, I'm just quoting the dictionary
toodles