Sunday, November 20, 2011 
Sour foods are acidic, and include certain fruits (e.g., lemons, oranges, and grapes), and some fermented foods, like wine and yogurt.
Various chemicals are perceived as tasting bitter. Bitter foods include some vegetables, (e.g., endives, spinach, and cabbage), and also cocoa, coffee, tea, beer, and tonic water. Bitter compounds are often toxic, so people are especially sensitive to bitter flavors.
Thursday, August 11, 2011 Coal is a dark brown to black rock formed when plant matter is buried and exposed to pressure over geologic time spans. Coal, which consists primarily of carbon, is a fossil fuel that is burned to generate electricity.
Like coal, charcoal is a solid black fuel made mostly of carbon. Charcoal is made by heating wood or other organic substances in the absence of air. Charcoal is also used in drawing, and to absorb odors, gases, and toxins. While coal is usually mined, charcoal is manufactured.
Tuesday, August 2, 2011 An ancestor is a relative who lived in the past, especially one more remote than a grandparent. Ancestor is synonymous with forebear or progenitor. A descendant is the progeny, however remote, of a specific ancestor. Descendant is synonymous with offspring or scion. A great-grandparent is an ancestor; a great-grandchild is a descendant.
Sunday, July 17, 2011 Biannual is synonymous with semiannual. They both mean ‘happening twice a year’, e.g., in February and August. Biennial events, like the Olympics, happen every two years. Biennial plants have a life cycle that requires two years to complete.
Wednesday, July 6, 2011 A podium is a small raised platform used to elevate a speaker, an orchestra conductor, or the winners in a sporting event. A lectern is a stand with a sloped top, used by a lecturer or a member of the clergy to hold books, notes, or other materials used during a presentation. One stands on top of a podium, and behind a lectern.