> (Btw, bananas are berries, but cows are not deers. :) )

Not sure if you're joking or not, but to be clear to non-native speakers: bananas are definitely not berries. Berries are smaller and rounder. For example: blueberries, raspberries, blackberries. I guess strawberries, too, but they're outliers.

Also the plural of deer is deer.

Bananas ARE berries, so are watermelons and tomatoes. But strawberries and raspberries are not berries.

Berries have seeds on the inside; a strawberry's seeds are on the outside, and raspberries are little clusters they are called something else. It's a famous quiz question in the UK :)

It depends, of course, if you're talking as a botanist or as a cook. It's one of those words with multiple levels of truth.

Same with tomato - it's a fruit botanically, but in culinary terms it's a vegetable and definitely not a fruit. As long as you get your context right, you won't have problems communicating :)

Wikipedia suggests bananas are berries, at least under some definitions of 'berry':

http://en.wikipedia.org/wiki/Berry

Actually, you can refer to a female deer as a "cow" (though "doe" is more common).