Is New York City Considered An Island Or Peninsula?

My sun has to make homework for school and he asked me if New York City is considered an island or a peninsula and I truly don't know. I was searching but I don't understand what is the difference. I know I've studied about the islands and peninsulas at school but I forgot everything so now I can't tell my sun how is considered New York City. I would like to know more about all these things but I don't have time to read a lot of websites, so if you can help me it would be great.
Is New York City considered an island or a peninsula?

Hi, it's really easy to know if it's an island or a peninsula and I'll explain it to you in a very simple way and you will understand why is New York City considered a peninsula. An island is any piece of sub-continental land surrounded by water, and New York City is not completely alone, it's connected with the rest of the country, so it doesn't follow this rule, while a peninsula is a piece of land bordered by water on three sides but connected to mainland.
Inside New York City there are islands, like Manhattan or Long Island, but the city itself is a peninsula.