In organic chemistry, a Schiff base (named after Hugo Schiff) is a compound with the general structure  ( = alkyl or aryl, but not hydrogen). They can be considered a sub-class of imines, being either secondary ketimines or secondary aldimines depending on their structure.   Anil refers to a common subset of Schiff bases: imines derived from anilines.  The term can be synonymous with azomethine which refers specifically to secondary aldimines (i.e.  where R' ≠ H).