One school of thought is that the fruit of a plant contains its seeds: apples, pears, peaches, oranges, bananas, mangoes, kiwis, cucumbers, and tomatoes are examples of fruits. Yes, cucumbers and tomatoes are fruits!...or so this line of thinking goes. Technically, a tomato is a berry, like a grape (most people don't think of grapes as berries). This school of thought further asserts that vegetables are generally everything else -- the leaves, stalks, stems (including tubers), roots, etc. However, Dictionary.com indicates that essentially the terms "fruit" and "vegetable" are interchangeable. "Vegetable" is the fruit, stem, foliage, tuber, etc., that can be consumed as food. "Fruit" is merely the product of plant life that is useful to humans or animals. Further, though, in everyday American life, the term "fruit" is used to refer to plant products that have a high sugar content or sugary taste. "Vegetable" on the other hand tends to be used in connection with plant products that are more savory, or are prepared and served with more savory dishes. For instance, most people consider tomatoes and corn as "vegetables", and even though they generally have a "sweet" taste, they are typically prepared or paired with savory meal items. Although this is not a fool-proof distinction, it is how North American society's language has evolved the meanings of the two words, and how we in actuality distinguish "vegetable" from "fruit", even though in their most basic meanings they are actually interchangeable. Even though nuts and grains can be technically referred to as either "fruit" or "vegetable", American society consistently places both of these in their own separate food categories, neither as fruit or vegetable. In short, it is technically correct to refer to any consumable plant product as either fruit or or vegetable, but you'll get very strange looks if you refer to bread or spinach as "fruit", or to a banana or orange as a "vegetable". There are plenty of "experts" that will smugly proclaim that a peanut is "tuber" or legume, while most of us consider it a "nut". Most folks think of avocado as a "vegetable" because we eat it almost invariably with savory dishes, but it grow on a tree, so other "experts" declare it a "fruit" -- both are correct by the dictionary.com definition. So knock yourself out, call them what you may -- in the end all can be referred to technically as fruits or vegetables, but there's of course no shortage of opinions to the contrary.
Considered a fruit. When you think of veggies- so many contain seeds that it makes sense the term would be interchangeable. Okra, cucumbers, peppers- all contain seeds but are considered generally up be veggies.