"Veganism" Is Different From A "Vegan Diet"
You can eat a vegan diet without being vegan, but you cannot be vegan without eating a vegan diet. Veganism and a vegan diet are related, but they are not the same thing, for veganism is more than what we eat.
The Vegan Society defines veganism as follows:
"Veganism is a philosophy and way of living which seeks to exclude—as far as is possible and practicable—all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of animals, humans and the environment. In dietary terms it denotes the practice of dispensing with all products derived wholly or partly from animals."
So, as you can see, diet is certainly a big part of veganism, but in truth, veganism is a "philosophy" and a "way of living" that seeks to avoid all forms of animal exploitation and cruelty to animals. Raising animals for food is certainly the most prevalent form of this exploitation and animals suffer greatly because of it (as outlined in other parts of this website). But there are many other practices that cause great harms to animals that have nothing to do with diet, and veganism (and vegans) seek to avoid all of these forms of cruelty and exploitation.
Professor Gary L, Francione, in his book, Why Veganism Matters, and himself a vegan for over 40 years, defines veganism as follows:
"Veganism involves not eating, wearing, or using animals or animal products to the extent practicable with the goal of abolishing all animal use because such use cannot be morally justified."
If you eat a vegan diet but your only reason for doing so is for your health, such that you also buy/wear animal byproducts, such as leather, and/or go to zoos, rodeos, and circuses, and/or buy/use personal hygiene products that either contain ingredients derived from animals or that were tested on animals, then you are not "vegan" even though you do eat a vegan diet.
But like I said above, while it is possible to eat a vegan diet and not be vegan, it is NOT possible to be vegan without eating a vegan diet. So, if you mostly eat a vegan diet, but sometimes eat cheese or eggs, this is not actually a vegan diet and you cannot say that you are vegan. (Please note that I am saying this factually and not judgmentally, even though my personal judgement is that everyone should become morally vegan.)
Please consider truly going vegan and helping to end ALL forms of animal exploitation and cruelty.
Mahalo for reading. Aloha...