The answer to this is both yes and no. Some antioxidants are vitamins and vice versa, but this is not always the case. For example, Vitamin C and E are antioxidants and vitamins, but vitamin D is only considered a vitamin. There are thirteen essential vitamins, and by contrast there are thousands antioxidants.
What is an Antioxidant?
The science behind this is quite complicated but, put simply, the universe is composed of tiny pieces called molecules. At this extremely small level, there are what are called "free radicals" which are unstable molecules that "grab" bits of electric charge from other molecules in order to become more stable. Free radicals damage the cells of your body and can contribute to the development of a number of deadly diseases. Antioxidants prevent or inhibit free radicals from doing this by giving up some of their own charge, thereby helping to protect the cells of your body, and inhibiting the development of many diseases.
What is a Vitamin?
A vitamin is something that a living thing requires (in limited amounts) to live. For humans, there are thirteen vitamins that are essential. These vital vitamins are vitamin A, vitamin C, vitamin D, vitamin E, vitamin K and the group of B vitamins, which include: thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, vitamin B12 and folate. Of these, only vitamin C and E are antioxidants; although many of the others aid in the formation or maintenance of antioxidants. Vitamin A, for example, has many antioxidant properties, but can be toxic if over-consumed.