Microbes are the part of our lives in more ways than most understand. They have shaped the present environment and their activities will greatly influence our future. Microbiology is one of the most applied of all the biological sciences. It is the study of bacteria, including their classification and the prevention of diseases that arise from bacterial infection. The subject matter of bacteriology is distributed not only among bacteriologists but also among chemists, biochemists, geneticists, pathologists, immunologists and public-health physicians. The science of microbiology is subdivided into a number of diverse fields: Bacteriology is the study of the bacteria, Virology the study of viruses, Protozoology the study of protozonas, Phycology the study of algae, and Mycology is the study of fungi. The important applied fields of microbiology are Medical microbiology, Aquatic microbiology, Aero-microbiology, Soil and Agricultural Microbiology, Industrial microbiology, Exo-microbiology, Geochemical microbiology, Food microbiology, Water and Wastewater microbiology, etc. Microbiology overlaps with number of scientific disciplines including biochemistry, genetics, zoology, botany, ecology, pharmacology, medicine, food science, agricultural sciences, industrial science, environmental science, etc. The fields, vistas and challenges for the student of microbiology are virtually limitless, and new discoveries are made daily. Microbiology is an exciting and challenging field of science for students and professionals alike. The present Dictionary is prepared for Under and Post Graduate students of all universities. I am sure that the present work will be useful for the students of Microbiology, Biological, Agricultural, Medical, Veterinary, Home science and Environmental science students all over India.