I think the terms are used quite loosely. For instance, the subjective “acidity” has little to do with the actual acidity in the brew. Out of interest, I measured the acidity of this morning’s espresso with pH paper. My tap water is pH 6.75 (very slightly acidic compared with neutral pH 7.0). The coffee was pH 6.5 . For comparison, table vinegar was completely off the scale blow pH 4.0 . Even when the vinegar was diluted 100:1 it was still below pH 4.0.
So coffee is less that 1/100th as acidic as table vinegar. I don’t think anyone’s taste buds are going to tell the difference in actual acidity between two cups of coffee.
When I taste my morning espresso, the things I focus on are
- Body: does the coffee coat all parts of my tongue with flavor? ?
- Bitterness: Does the coffee “bite” the side edges of my tongue? A bit of bite is OK.
- Legs: How long does the taste last and how does the flavor develop during that period?
A great coffee offers flavor to your entire mouth and the flavor changes and develops for at least 30 seconds after a sip. A miserable coffee leaves you with no flavor after a few seconds… except a bitter bite on the edges of your tongue.