| Word | Description |
| R-Value | refers to a window assembly's resistance to heat flow; R-Value is the inverse of U-Factor (U=1/R) i.e., if the R-value of a window assembly is 2, the U-Factor is 0.5. |
| Reclaimed Water | Pinellas County’s reclaimed water is highly treated wastewater produced through an advanced wastewater treatment process. This process eliminates any harmful byproducts while retaining beneficial elements, such as nitrogen, for irrigating landscapes. |
| Red Meat | Red meat in culinary terminology refers to meat which is red-colored when raw, while in nutritional terminology, it refers to meat from mammals. In nutrition, "red meat" is synonymous with "mammal meat." The term is often considered misleading, as not all mammal meat appears red, and some non-mammal meat can be red. Red meat does not refer to how well a piece of meat is cooked or its coloration after cooking. A steak or hamburger is a red meat whether it is served rare, or cooked until it is well-done; pork is also red, though it turns to a whitish color when cooked. According to the USDA all meats obtained from "livestock" are "red meats" because they contain more myoglobin (an iron-containing pigment in muscle cells that holds and stores oxygen) than chicken or fish. |
| Refined grains | In contrast to whole grains, refined grains refers to grain products consisting of grains or grain flours that have been significantly modified from their natural composition. The modification process generally involves the mechanical removal of 2 of the 3 major parts of the grain: the bran and germ, either through grinding or selective sifting. Further refining includes mixing, bleaching, and brominating; additionally, thiamin, riboflavin, niacin, and iron are often added back in to nutritionally enrich the product. Because the added nutrients represent a fraction of the nutrients removed, refined grains are considered nutritionally inferior to whole grains. |
| Return-register or Grille | Picks up inside air for reconditioning, drawing the air through a changeable filter into the air handler of your central system |
| RGB | Red-Green-Blue, the three primary colors of light |
| Rootstock | The part of the graft combination which becomes the lower portion, or root, is termed the stock (understock, rootstock) |
| Rosette | The base of leaves where they join together, forming a flower-like appearance. |
| Roughage | A misleading term that is often used to describe the fiber content of a diet. It is coarse, indigestible plant food that stimulates intestinal contraction. |
| Russeting | Mites, especially rust mites and spider mites, feed on leaves and fruit, causing a variety of symptoms referred to as stippling, silvering and russeting. |
