Cheesecake Isn't Quite A Pie, And It's Definitely Not A Cake
Cheesecake is quite a deceptive dessert. Despite its name, it's not really a cake at all, even by using the loosest definition of a cake. However, at least the first part of the name is accurate; cream cheese, which makes up the bulk of the filling, is officially a type of cheese.
To explain why cheesecake isn't cake, we need to look at what defines a cake. Cakes are fundamentally flour-based baked goods while also using ingredients like baking powder or baking soda to make it rise, alongside butter (or another fat), eggs, and a liquid like milk to make a wet batter. Cheesecake falls short on at least two of these fronts. The base of cheesecake is not flour. Standard cheesecake recipes don't feature flour at all in the filling (which makes up the bulk of the final product). Granulated sugar, not flour, is what holds graham cracker crusts together. Also, cheesecake recipes don't use any leavening. Cheesecakes aren't always baked but when they are (for example, a New York-style cheesecake), there's nothing in the recipe to make them rise. They come out of the oven the same size as when they went in. Sure, cheesecakes can feature eggs and butter, but ultimately, a cake should have a drier, bready texture. Cheesecakes don't even come close.
Maybe cheesecake is a pie
Back in 2020, celebrity chef Alton Brown declared that cheesecake is a pie (not a cake). While he didn't get into the rationale for this argument, it seems to be at least partially right (although maybe not totally). At their simplest, pies are just a crust with filling on top and cheesecakes fit this bill. While cheesecakes might not always be prepared in a pie pan, this seems like a secondary issue. After all, it's possible to find fruity pies baked in sheet pans and other types of bakeware.
Regardless, cheesecakes still don't perfectly fit into the pie box. Think about a classic fruit pie (like cherry or apple) and there are some big differences to cheesecake. For one, pies are always baked. Even the dictionary definition of "pie" notes this. Meanwhile, it's relatively normal to have an unbaked cheesecake that simply sets in the refrigerator. On top of this, classic pies also have a layer of pastry on top of the filling, or at least a lattice. While there are certainly pies that don't have this (like key lime pie), they are usually baked, so they fall closer to the definition of a pie than cheesecakes. Perhaps key lime pies also fit in the same category as cheesecake, where they're neither cake nor pie.
Is cheesecake something else, then?
Maybe cheesecake exists outside of this cake-pie binary, creating a totally different dessert category of its own. One plausible explanation is that a cheesecake is a type of tart. The Oxford Dictionary backs this one up, describing a cheesecake as a "tart filled with curd or cream cheese." While tarts and pies are fairly similar, tarts don't have a pastry lid on top like a pie. So in this sense, cheesecakes fit into the same category. However, tarts do tend to be a shallower pastry, particularly in comparison to your average cheesecake, so that's one point against cheesecakes being tarts.
It's also been suggested that cheesecakes are a type of flan. There's some truth here in that cheesecake filling is a bit more like a custard than your average tart or pie filling. However, some flans also don't have a crust at all, so again, cheesecakes don't perfectly fit the bill.
It might sound wild, but perhaps a cheesecake doesn't perfectly fit into any dessert category. It's definitely not a cake; it's a bit like a pie and a bit like a tart. As long as it's delicious, that's what counts.