The gallon (abbreviation "gal"), with the US and imperial gallon, is a measure of volume. Historically it has had many definitions, but there are three definitions in current use: the imperial gallon (≈ 4.546 L) which since metrication is used colloquially in the United Kingdom and semi-officially within Canada, the United States (liquid) gallon (≈ 3.79 L), and the lesser used US dry gallon (≈ 4.40 L). The gallon, be it the imperial or US gallon, is sometimes found in other English-speaking countries.

There is one gallon defined in the imperial system but two (liquid and dry) in the US customary system.

The imperial (UK) gallon, defined as 4.54609 L, is used in some Commonwealth countries and was originally based on the volume of 10 pounds of water at 62 °F (17 °C). (A US liquid gallon of water weighs about 8.33 pounds at the same temperature.) The imperial fluid ounce is defined as ¹⁄₁₆₀ of an imperial gallon.

This gallon is defined as 231 cubic inches, and is equal to exactly 3.785411784 litres or about 0.13368 cubic feet. This is the most common definition of a gallon in the United States. The US fluid ounce is defined as ¹⁄₁₂₈ of a US liquid gallon.

Oprah Winfrey (born Orpah Gail Winfrey; January 29, 1954) is an American media proprietor, talk show host, actress, producer, and philanthropist. Winfrey is best known for her self-titled, multi-award-winning talk show, which has become the highest-rated program of its kind in history and was nationally syndicated from 1986 to 2011. She has been ranked the richest African-American of the 20th century, the greatest black philanthropist in American history, and was for a time the world's only black billionaire. She is also, according to some assessments, the most influential woman in the world.

Winfrey was born into poverty in rural Mississippi to a teenage single mother and later raised in an inner-city Milwaukee neighborhood. She experienced considerable hardship during her childhood, claiming to be raped at age nine and becoming pregnant at 14; her son died in infancy. Sent to live with the man she calls her father, a barber in Tennessee, Winfrey landed a job in radio while still in high school and began co-anchoring the local evening news at the age of 19. Her emotional ad-lib delivery eventually got her transferred to the daytime-talk-show arena, and after boosting a third-rated local Chicago talk show to first place, she launched her own production company and became internationally syndicated.