The confusion about 'fruit' and 'vegetable' arises because of the differences in usage between scientists and cooks. Scientifically speaking, a tomato is definitely a fruit. True fruits are developed from the ovary in the base of the flower, and contain the seeds of the plant (though cultivated forms may be seedless). Blueberries, raspberries, and oranges are true fruits, and so are many kinds of nut.
科学家和厨师们对西红柿用法的差异常常引起人们的疑惑，这货到底是水果还是蔬菜？科学来讲，西红柿就是水果。水果就是在花的子房里发育而成，含有植物的种子（尽管发育而成后的果实有可能是无籽的）。蓝莓，树莓，以及橙子都是水果，很多种类的坚果也是水果。

蓝莓、树莓、橙子……好多水果！爱吃水果的你，能用英语叫出多少种水果的名字？
快来看看这些水果的英语你有没有全部get~
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As far as cooking is concerned, some things which are strictly fruits, such as tomatoes or bean pods, may be called 'vegetables' because they are used in savoury rather than sweet cooking. The term 'vegetable' is more generally used of other edible parts of plants, such as cabbage leaves, celery stalks, and potato tubers, which are not strictly the fruit of the plant from which they come. Occasionally the term 'fruit' may be used to refer to a part of a plant which is not a fruit, but which is used in sweet cooking: rhubarb, for example.
而从烹饪的角度上来看，一些严格意义上属于水果的食物比如说西红柿和豆荚，就被视为蔬菜。因为它们被用来烹饪做成菜肴而不是做成甜食。蔬菜更广泛地用于其他植物可食用的部分，如卷心菜的叶子，芹菜的茎以及马铃薯块茎，这些从严格意义上来说都不是所属植物的果实。有时候水果还可以用来指用于制作甜食但是非植物果实的部分，比如说大黄。

So, the answer to the question is that a tomato is technically the fruit of the tomato plant, but it's used as a vegetable in cooking.
所以说，问题的答案就是，从技术上来说，西红柿是西红柿植株的果实，但是在烹饪上被用作蔬菜。