Appendix: Units and Constants

The standard international (SI) units are summarized in Table 20.1. Alternate units frequently used in medicine are indicated in subsequent comments. Often, units are given with a prefix, such as 1 mJ = 1 milliJoule = 10–3 J. Metric prefixes are listed in Table 20.2. Photometric units are dealt with in a separate section (Sect. 20.2).