This book gives a concise overview of measures of relationship, including measures of nominal-nominal association, ordinal-ordinal association, interval-interval correlation, nominal-ordinal association, nominal-interval association, ordinal-interval association, and agreement. The book emphasizes permutation statistical methods under the Fisher--Pitman model. However, the permutation analyses are always paired with conventional statistical analyses under the classical Neyman--Pearson model. The pairing allows for comparisons and contrasts between permutation and conventional analyses. Example analyses highlight the differences between the various measures and the permutation and conventional probability values. This book is a companion volume to  Permutation Statistical Methods: Tests of Differences by the same authors.