The odds ratio is the general term for the ratio of a particular outcome given two different conditions. For example how much more likely a person is to get type 2 diabetes if they are obese, compared with if they are of a lower weight. The Bayes factor is a particular example of an odds ratio, where it is used as a measure of the strength of evidence between hypotheses.
Defined on page 75
Used on pages 12, 75, 76, 77, 79