Group theory is conventionally taught in a one-semester course at the senior/graduate level for science students. For such a purpose, many textbooks, dealing with rigors of derivations and theorems, have been written to give in-depth treatment. For one reason or another, scientists with no prior knowledge of group theory may need quick familiarity with the subject, without mathematical derivation rigors. This book has been written for this purpose, based on lecture notes given to senior/graduate students who need to deal with bonding theories and spectroscopy, without pre-knowledge of group theory.