Sugar
In non-scientific use, the term sugar refers to sucrose (also called "table sugar" or "saccharose") — a white crystalline solid disaccharide. Humans most commonly use sucrose as their sugar of choice for altering the flavor and properties (such as mouthfeel, preservation, and texture) of beverages and food. Commercially-produced table sugar comes either from sugar-cane or from sugar-beet.
Scientifically, sugar refers to any monosaccharide or disaccharide. Monosaccharides (also called "simple sugars"), such as glucose, store energy which biological cells use and consume.
Under an optical microscope at low power, sugar will look like a bunch of messy shapes scattered all over. It will have fragments, other pieces sticking out from one another, and will differ in size and shape.
In a list of ingredients, any word that ends with "ose" will likely denote a sugar. Sometimes such words may also refer to any types of carbohydrates soluble in water.
In culinary terms, the foodstuff known as sugar delivers one of the primary taste sensations, that of sweetness.
Source: Wikipedia