1. n. in regression analysis, the difference between the value of an empirical observation and the value predicted by a model. Analysis of residuals allows a researcher to judge the fit or appropriateness of the model for the data.

2. adj. denoting a condition in which acute symptoms have subsided but chronic or less severe symptoms remain.

3. adj. denoting remaining ability (e.g., residual hearing) or a remaining disability (e.g., residual loss of vision) after a trauma or surgery.