This is a major revision of a classic, best selling reference book. Originally published by the American Institute of Physics under the title "Physics Vade Mecum" in 1981, and then the second edition in 1989 with the new title "A Physicist's Desk Reference", this third edition has been completely updated and modernized to reflect current modern physics.The book is a concise compilation of the most frequently used physics data and formulae with their derivations. This revision has six more chapters than the second edition, outdated chapters dropped, and new chapters added on atmospheric physics, electricity and magnetism, elementary particle physics, fluid dynamics, geophysics, nonlinear physics, particle accelerators, polymer physics, and quantum theory. There is a new last chapter on practical laboratory data. The references and bibliographies have been updated.