             Oblique Factor Rotation Factor rotation computed so that the extracted factors are correlated. Rather than arbitrary constraining the factor rotation to an orthogonal solution, the oblique rotation identifies the extent to which each of the factors are correlated.

 On-Line Methods of parameter estimation adjust the estimate after each new example is seen.

 Ordinal Feature An ordinal measurement is one of a series of ordered categories , for example income ('poor', 'sufficient', 'well-off', 'rich...').

 Orthogonal(Factor Analysis Only) Mathematical independence(no correlation) of factor axes to each other (i.e., at right angle, or 90 degrees).

 Orthogonal Factor Rotation Factor rotation in which the factors are extracted so that their axes are maintained at 90 degrees. Each factor is independent of, or orthogonal to, all other factors. The correlation between the factors is determined to be 0.

 Outliers Outliers are examples which did not (or are thought not to have) come from the assumed population of examples. For example, in digit recognition, the segmentation will fail occasionally, so the data will not be from a digit at all. 