Short Definition
A feature is an input signal used by a model to make a prediction or learn a representation.
Intuition
Features are the pieces of information a model gets to see. Better features often make the learning problem easier.
Technical Definition
A feature is a measured, engineered, or learned variable supplied to a model as part of its input vector, tensor, or structured input.
Example
For a loan-risk model, income, credit history, and debt ratio may be features.
Common Misunderstandings
Features are not always hand-designed; deep models often learn them.
A feature can be predictive without being causal.