Avocados are definitely fruits botanically. They are the ripened ovaries of the avocado tree and contain seeds. Interestingly, they are technically a berry instead of a drupe because there is a very thin endocarp (third layer of fruit) around the stone.
Culinarily, they’re…well…I’m honestly not sure. I would personally think of them more as a vegetable because they’re not really sweet and they’re more substantive. But apparently some people do eat them as a fruit or in a fruit salad, especially in Africa, so…who knows. ¯\_(ツ)_/¯
As long as you don’t say that they are fruits because of the botanical definition I’ll be happy.
The Supreme Court has offhandedly referred to avocados as fruit. This is persuasive, but not legally-binding. Also, the Supreme Court doesn’t decide the culinary definitions.