Acidity is diminished with increased roasting. Acidity is akin to the dryness of wine. Body is the feel of a beverage in the mouth, a sense of heaviness, richness, or thickness when tasting. Body ranges from light to full. It can be strong but pleasant.
Body is actually micro particles of insoluble coffee fiber suspended in water.
The amount and kind of insoluble varies from one coffee to another. Body also reflects the type of soil in which the beans were grown. Light coffees have a higher acidity, are light on the palette, and have higher notes. Medium coffees are a complex, spicy mixture of both ends of acidity. They have high notes with an earthy finish.