A banana is a curved, yellow fruit with a thick skin and soft sweet flesh. If you eat a banana every day for breakfast, your roommate might nickname you "the monkey."
A banana is a tropical fruit that's quite popular all over the world. It grows in bunches on a banana tree. To "go bananas" is a slangy way of saying "go crazy" or act ridiculous, and if someone refers to the "top banana," they mean the most important person in a particular group. The origin of banana isn't certain, but it's thought that it was borrowed by the Spanish or Portuguese from an African word, probably the Wolof word banana.