There is no mistaking a sweet potato.
You can’t eat one and wonder whether it is, perhaps, a zucchini. No one has ever sampled one and confused it with a turnip. It is impossible to take one for broccoli, or even a regular potato.
Sweet potato is a sweet potato is a sweet potato.
Its uniqueness is both its curse and its charm. Nothing else is quite like it, but that also means its utility is limited. It is not something you would ever want to use as a substitute for another ingredient. It is, as they say, what it is.
One thing it isn’t, incidentally, is a yam. Though both are root vegetables, they are unrelated (for that matter, sweet potatoes are only distantly related to our common potatoes). They don’t even look alike — yams resemble horseradish roots, and can grow to be more than 50 pounds — and yams are much less sweet, drier and starchier.
True yams are almost never sold in America, though you can sometimes find them in international markets. In general, if it is labeled either a yam or a sweet potato, it’s a sweet potato.