The tomato is not a citrus fruit. Tomatoes are actually nightshades; eggplant and potatoes are also included in this group. Citrus fruits include oranges, grapefruits and lemons.
One of the defining factors that proves that tomatoes are not citrus fruits is that citrus fruits grow on perennial trees. Tomatoes grow on vine plants. Although the plants may technically be considered perennials, tomatoes grow as annuals.
Tomatoes may reduce the risk of macular degenerative disease as they prevent serum lipid oxidation. The fruits are also high in lycopene, an antioxidant that can reduce the risk of prostate, cervical, colon and rectal cancers.