Is a tomato a fruit or vegetable? This is a tricky question, one that actually went all the way to the Supreme Court. 

In 1893, the question of whether a tomato was a fruit or a vegetable became a central issue in the case of Nix v. Hedden, a complex lawsuit involving tariffs. The court ruled that for the matter at hand, tomatoes were indeed a vegetable and not a fruit.

According to botanists, fruit have seeds. And because tomatoes have seeds, they classify them as fruit. What about cucumbers, squash, green beans and walnuts? They all have seeds, so do botanists consider them fruit? The answer is yes.

Most people consider tomatoes, as well as all the items listed above, to be vegetables -- with the exception of walnuts, of course. Many believe that tomatoes (and other plant foods with seeds) were labeled vegetables because they lack the sweetness normally associated with fruit. In addition, tomatoes are typically used as a vegetable in recipes and meals.

Dietitians and nutritionists classify tomatoes as vegetables, but for different reasons. From a nutrition standpoint, vegetables have less than half the calories per serving than fruit. This is one reason why tomatoes, cucumbers, squash and green beans fall into this category. Walnuts, on the other hand, are made up of 90 percent fat and less than 1 percent protein, which is why they are classified by dietetic professionals as a polyunsaturated fat, and not a fruit.