What is a fruit?

The craziest thing about my blog is the most frequently visited page: Artichoke - a fruit or vegetable? An awful lot of people must have lost sleep over this question because it has been my top ranked blog for the past 2.5 years, and this is hardly a seminal piece of botanical knowledge. However it does suggest that a more general explanation might be informative.
Flowering plants are composed of stems, leaves, and roots, and foods comprised of these parts are technically vegetables, the vegetative parts of plants. But here's the problem. Flowers are also composed of modified leaves borne on a modified stem, and when immature, usually in bud as in broccoli, they qualifiy as vegetables too. Fruits are flowers at the stage of seed dispersal, so fruits must also be modified leaves, but after post-pollination development has begun, they are categorized as fruits (and seeds). Thus the artichoke eaten prior to pollination still qualifies as a vegetable, and what is eaten is the succulent modified stem and the bases of the modified leaves (bracts) surrounding the inflorescence. A strawberry is actually quite similar in that the red fleshy tissue is actually the modified stem of the flower and the "seeds" are actually little dry fruitlets. Sometimes fruits from several flowers will fuse during development to produce multiple fruits: pineapple, mulberry. In these cases perianth parts become fleshy too contributing to the whole. Similar looking fruits can result when a single flower has many separate pistils producing aggregate fruits: raspberry, cherimoya. Some fruits are dry at maturity, although the fleshy types are more frequently and regularly thought of as fruits. Some fruits that are dry at maturity are eaten when they are immature and fleshy: beans and pea pods, okra. This means that many things thought of and eaten as vegetables are really fruits (sometimes including the seeds): cucumber, squash, green beans, snow peas, okra, tomato, peppers, eggplant, to name the more common ones. Confused? Well so is the USDA because they categorize vegetables based on common usage (To the USDA rhubarb is a fruit.) rather than the botanically correct definitions. That's good; it's terrible when your government goes and confuses itself by using science.