"Botanically, tomatoes are a fruit. This is because a fruit is the edible part of the plant that contains the seeds, while a vegetable is the edible stems, leaves, and roots of the plant. Commercially (and on our dinner plates) it's known as a vegetable."
"Nix v. Hedden, 149 U.S. 304 (1893), was a decision by the Supreme Court of the United States that affirmed the lower court ruling that the tomato should be classified under customs regulations as a vegetable rather than a fruit. The Court's unanimous opinion held that the Tariff Act of 1883 used the ordinary meaning of the words "fruit" and "vegetable," under which a tomato is classified as a vegetable, instead of the technical botanical meaning."
According to the strict definition of botany about fruit, tomatoes may be defined as fruit by most botanist , but fruit and vegetables have no obvious distinguish, only in accordance with people's habits to distinguish. Some people think is fruit, some people think that is a vegetable, I don't know the truth.