It shares many of the same qualities as cheese: it’s made from milk, it is aged, it is thickened, etc. Yet strangely, yogurt is not classified as a cheese. Sure it is more loose than typical cheese. But so is cottage cheese, and that is obviously a cheese. Why isn’t yogurt classified as a cheese? And if it isn’t a cheese, what is it?
From dictionary.com
cheese1 Audio pronunciation of “cheese” ( P ) Pronunciation Key (chz)
n.
yo·gurt also yo·ghurt or yo·ghourt Audio pronunciation of “yogurt” ( P ) Pronunciation Key (ygrt)
n.
A custardlike food with a tart flavor, prepared from milk curdled by bacteria, especially Lactobacillus bulgaricus and Streptococcus thermophilus, and often sweetened or flavored with fruit.(The below applies to traditional ways to make the products. “Processed cheese products” and such are a whole 'nother thing.)
Note that rennet is added to milk to produce the curds which are then removed, pressed, etc. to make cheese. Along the way cultured bacteria are added and the cheese is aged. Aging can take months (esp. with drier cheeses). The whey is not used.
For yogurt, the complete milk is used and the bacteria alone modify it. Aging takes just a few days.
Note that the most similar product to yogurt is buttermilk.
As has been mentioned, yogurt doesn’t involve removing whey they way cheese does. So now I’m curious: how about cottage cheese and very soft cheeses? Do they have the whey removed less thoroughly? Or do the specific bacterial processes just result in a different consistency in those things? Is the curdling and pressing process significantly different between different sorts of cheeses, or is it just the bugs and the source of the milk that make cheddar and feta and stilton and brie so different?