And they're probably not the sizes you're thinking
As my profile says, I am a coffee snob. That is to say, I like good coffee, I know many ways of serving coffee and the commonplace quick brewed grounds that have been sitting too long in a ground state taste awful to me.
As a coffee snob, I grumble at the Starbucks convention of calling sizes "Tall", "Grande" and "Venti". Not only are these in different languages, they're entirely wrong.
Coffee should be served in three sizes, "demitasse" (black), "tasse" (black or sweetened), and "au-lait" (with milk). Tea is served in two sizes, "tasse" or "Milk Tea".
Demitasse
These tiny teacups are not for tea at all, they are for tisanes and cordials. Coffee is a tisane, a flavored brew made from something other than tea leaves. The demitasse, or half-cup, is four ounces in size and intended for sampling the rich strong flavor of coffee, cordials and other tisanes.
Tasse
Although you would expect it to be eight ounces, the standard teacup is either six or eight ounces in size and called a tasse (french for cup). This is the standard size for black tea or sweetened tisanes. Typically you will not find milk in a tasse.
Milk Tea
Milk Tea is served in a 12 ounce cup. The serving is 8 ounces of tea and 3 ounces of warm milk. Traditionally this is a social afternoon tea served with biscuits (cookies) and other small treats. Coffee does not have a 12 ounce size.
Au Lait
Au Lait means with milk. Coffee in a 14 or 16 ounce bowl cup that is 12 ounces of coffee and 2 ounces of hot milk is "Au Lait". Many cultures, including Americans and Italians have adopted this size. In America, two ounces of espresso (pressed coffee) is used in an au lait or cappuccino instead of the percolated "drip" coffee or an infusion.
