Feature
A measurement on an example, so the training set of examples has measured features and a class for each.
 
 
     
 
  Feature Extraction
Creating useful new features by combinations (usually linear) of existing features.
 
 
     
 
  Feed-Forward Network
A network in which vertices can be number so that all connections go from a vertex to one with a higher number. In practice the vertices are arranged in layers, with connections only to higher layers.