The k-nearest neighbor or kNN algorithm falls into a category of machine learning algorithms that are called "lazy learners" as opposed to other predictive analytics tools (such as decision trees or logistic regression or neural network models) which are called "eager learners". Why is that?

We have discussed two types of classification techniques previously: decision trees and logistic regression. This article introduces, in basic terms, a third classification technique called k-nearest neighbors or k-NN.