This needs-based book summarizes important correlations about interpretation of structures — i.r. frequencies (both theoretical and experimental) from a vast amount of data available in a number of excellent encyclopedic books. It contains a short elementary introduction on the calculation methodology for Normal Co-ordinate Analysis that will aid students in assigning a particular band to a functional group or normal mode. Statistical correlations of the i.r.-frequency data are dealt with in a number of examples not found in most other books. This book also details various spectroscopies with different optics and strategies for analyzing the spectron. Students will also get ample practice with a comprehensive section containing more than 350 problems and worked-out solutions.