What does acidity mean in coffee?

When coffee people talk about acidity, they don't mean the kind that upsets your stomach. They mean the bright, lively quality you get in a well-grown, carefully processed coffee - the sensation that makes it feel crisp and alive on the palate rather than flat and dull.

Chemically, this comes from organic acids - primarily citric, malic, phosphoric, and tartaric - that develop within the cherry as it matures. Higher altitude slows that maturation down, giving more time for these acids to form. It's why coffees from 1,800 masl in Ethiopia or Colombia's Huila tend to taste more vibrant than lower-grown equivalents from the same region.

Roasting progressively suppresses acidity as heat breaks down acidic compounds - a lighter roast preserves it, a darker roast softens or eliminates it. On the SCA cupping form, acidity is scored separately for intensity and quality, because bright acidity well-expressed is one of the clearest markers of exceptional green coffee. It can't be added later. If it's not in the green, no amount of careful roasting will put it there.