The Penguin Dictionary of Biology defines some 6,000 terms relating to this rich, complex, and constantly expanding subject—from amino acids, bacteria, and the cell cycle to X-ray diffraction, Ychromosomes, and zygotes. Long established as the definitive single-volume source, the dictionary has now been extensively updated for its eleventh edition. With expanded encyclopedic entries to explain the most crucial concepts, it explores the very latest discoveries and developments, containing more than 400 new entries to take account of the latest thinking on genetics, human physiology, disease, and cell biology. All key botanical and zoological concepts as well as the core vocabulary of biochemistry, immunology, evolutionary theory, and ecology are defined in depth, making this the ideal reference for students, teachers, professionals, and amateur biologists.