Biology (from Greek βιολογία - βίος, bios, "life"; -λογία, -logia, study of) is the science that studies living organisms. Prior to the nineteenth century biology came under the general study of all natural objects called natural history. The term biology was first coined by the French naturalist Jean-Baptiste Lamarck. It is now a standard subject of instruction at schools and universities around the world, and over a million papers are published annually in a wide array of biology and medicine journals.

Biology examines the structure, function, growth, origin, evolution, distribution and classification of all living things. Five unifying principles form the foundation of modern biology: cell theory, evolution, gene theory, energy, and homeostasis.

Traditionally, the specialized disciplines of biology are grouped by the type of organism being studied: botany, the study of plants; zoology, the study of animals; and microbiology, the study of microorganisms. These fields are further divided based on the scale at which organisms are studied and the methods used to study them: biochemistry examines the fundamental chemistry of life, molecular biology studies the complex interactions of systems of biological molecules, cellular biology examines the basic building block of all life, the cell; physiology examines the physical and chemical functions of the tissues and organ systems of an organism; and ecology examines how various organisms interrelate with their environment.