A tannin (also known as vegetable tannin, natural organic tannins or sometimes tannoid, i.e. a type of biomolecule, as opposed to modern synthetic tannin) is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.

The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather. However, the term "tannin" by extension is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with proteins and other macromolecules.

The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also as pesticides, and in plant growth regulation. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine. Likewise, the destruction or modification of tannins with time plays an important role in the ripening of fruit and the aging of wine.

Gerald McCoy (born February 25, 1988) is an American Football defensive tackle for the Tampa Bay Buccaneers of the National Football League (NFL). He played college football for the University of Oklahoma, and earned consensus All-American honors. McCoy was the third pick overall in the 2010 NFL Draft.

McCoy was born in Oklahoma City, Oklahoma. He prepped at Southeast High School in Oklahoma City. After notching 83 tackles, including 23 tackles for loss and 20 sacks, he was named All-area, all-state and all-metro as a junior in 2004. As a senior he logged 82 tackles, 20 sacks and recovered nine fumbles. McCoy received numerous awards including 2005 National Defensive Player of the Year by USA Today. He was ranked as the top defensive tackle of the class of 2006 by a number of recruiting services, including Rivals.com. Following his senior season, McCoy was invited to play in the 2006 U.S. Army All-American Bowl.

McCoy attended the University of Oklahoma, where he played for coach Bob Stoops' Oklahoma Sooners football team from 2006 to 2009. As a a junior and senior, he was a first-team All-Big 12 selection in consecutive years. As a junior in 2008, he was a first-team All-American; as a senior in 2009, he was recognized as a consensus first-team All-American.