Short Definition
Regularization is any technique that constrains learning to reduce overfitting and improve generalization.
Intuition
Regularization keeps the model from using unnecessarily complicated explanations when a simpler pattern is likely to work better.
Technical Definition
Regularization modifies the training objective, architecture, or data process to prefer solutions with desired properties such as small weights, sparsity, or robustness.
Example
L2 regularization penalizes large weights so a model relies less on extreme parameter values.
Common Misunderstandings
Regularization is not only one formula; it is a family of techniques.
Too much regularization can cause underfitting.