There are still a lot of misconceptions about walnuts being vegetables when in reality they are not. Nuts are simply a hard-shelled form of fruit. You will find that there are many different types of nuts, including hickory nuts, chestnuts, hazelnuts, Brazil nuts, and walnuts.
A lot of “nuts” are actually just kernels or seeds, despite what many people may think. Nuts that are nothing more than seeds include cashews as well as Brazil nuts and pistachios. Walnuts in particular are nothing more than a hard-shelled fruit, putting to rest the notion that they are actually a vegetable.