# Deviation

**Deviation** used in many context in SuperMemo usually stands for root-mean-square deviation (RMSD) or residual. The root mean square (RMS) is the square root of the mean square (i.e. quadratic mean).

See: RMSD @ Wikipedia

Exemplary application in SuperMemo:

- Search for a universal memory formula
- SuperMemo Algorithm: 30-year-long labor
- Algorithm SM-17
- Memory consolidation
- R-Metric
- quantifying fitness of approximation procedures (e.g. see Stabilization decay)

This glossary entry is used to explain SuperMemo, a pioneer of spaced repetition software since 1987