Carbohydrate
Definition
Sugars and starches: the body's quick energy source, built from carbon, hydrogen, and oxygen.
Technical definition
Carbohydrates are biomolecules of carbon, hydrogen, and oxygen (roughly Cn(H2O)n) including monosaccharides (glucose), disaccharides (sucrose), and polysaccharides (starch, cellulose, glycogen). They serve as energy sources and structural materials.
Example
Glucose fuels your cells, starch stores energy in plants, and cellulose builds plant cell walls: all carbohydrates, very different jobs.
Common confusion
Carbs are not one thing. Glucose dissolves instantly for quick energy while cellulose is indigestible fiber: the category spans sugars to wood.