Taste those high, thin notes, the dryness the coffee leaves at the back of your palate and under the edges of your tongue? This pleasant tartness, snap, or twist, combined with an underlying sweetness, is what coffee people call acidity. It should be distinguished from sour or astringent, which in coffee terminology means an unpleasant sharpness. The acidy notes should be very clear, powerful and transparent in the Costa Rica, rich and wine- or berry-toned in the Kenya, and deeper-toned and muted in the Sumatra. They should be drier in the Costa Rica and perhaps a bit sweeter in the Kenya. Robustas and some lower-grown arabica coffees may display virtually no acidity whatsoever and consequently taste flat.
You may not run into the terms acidity or acidy in your local coffee seller's signs and brochures. Many retailers avoid describing a coffee as acidy for fear consumers will confuse a positive acidy brightness with an unpleasant sourness. Instead you will find a variety of creative euphemisms: bright, dry, sharp, brisk, vibrant, etc.
An acidy coffee is somewhat analogous to a dry wine. In some coffees the acidy taste actually becomes distinctly winy; the winy taste should be relatively clear in the Kenya. In promotional tags you may find the tones that I call winy described with other terms: fruity, dry fruit, and various specific fruit names, particularly berry and black current. The main challenge is to recognize the fundamental complex of fruit and wine-like sensations; once you do that, you can call them anything you like.
Body or mouth-feel is the sense of heaviness, tactile richness, or thickness when you swish the coffee around your mouth. It also describes texture: oily, buttery, thin, etc. To cite a wine analogy again, cabernets and certain other red wines are heavier in body than most white wines. In this case wine and coffee tasters use the same term for a similar phenomenon. All of the sample coffees I recommend should have relatively substantial body -- either the Costa Rica or the Sumatra will be the heaviest and the Kenya -- usually a medium-bodied coffee -- the lightest. In terms of texture or mouth-feel the Sumatra may display the most interest -- perhaps an oily or gritty sensation. But avoid inventing something you fail to taste. None of these coffees will be thin-bodied or anemic.
Strictly speaking, aroma cannot be separated from acidity and flavour. Acidy coffees smell acidy, and richly flavoured coffees smell richly flavoured. Nevertheless, certain high, fleeting notes are reflected most clearly before the coffee is actually tasted. There is frequently a subtle floral note to some coffee that is experienced most clearly in the aroma, particularly at the moment the crust is broken in the traditional tasting ritual. Of the three coffees I recommend for your tasting, you are most likely to detect these fresh floral notes in the Kenya, but depending on the roast and freshness of the coffee you could experience it in any of the three samples. Latin-American coffees brought to a medium roast, like the Costa Rica, may display a sweet vanilla-nut complex in aroma. The Sumatra also may exhibit smoky, pungent, earthlike, or spicy notes. Finally, if your Costa Rica is a La Minita, the aroma should have a sort of echoing, resonant depth to it. The same should be true of the Kenya, whereas you may find that the aromatic sensations of the Sumatra are rather immediate and limited, without a sense of dimension opening behind and around them.
If aroma is the overture of the coffee, then finish is the resonant silence at the end of the piece. Finish is a term relatively recently brought over into coffee tasting from wine connoisseurship. It describes the immediate sensation after the coffee is spit out or swallowed. Some coffees develop in the finish -- they change in pleasurable ways. All three of the sample coffees I recommend should develop in the finish. I would predict that the pungent tones of the Sumatra may soften toward cocoa or chocolate in the finish, and the dry wine or berry tones of the Kenya turn sweeter and fruitier.
Flavour is a catch-all term for everything we do not experience in terms of the categories of acidity, aroma and body. In another sense, it is a synthesis of them all. Some coffees simply display a fuller, richer flavour than others, are more complex, or more balanced, whereas other coffees have an acidy tang, for instance, that tends to dominate everything else. Some are flat, some are lifeless, some are strong but mono-toned. We also can speak of a distinctively flavoured coffee, a coffee whose flavour characteristics clearly distinguish it from others.
The following are some terms and categories often used to describe and evaluate flavour. Some are obvious, many overlap, but all are useful.
The following terms often come up informally in discussions of espresso coffees, though more as terms of connoisseurship than of trade. They relate as much to the effects of brewing and roasting as to the qualities of the original green bean and are less clearly defined than the technical tasting terms defined earlier.