Machine LearningNature is a self-made machine, more perfectly automated than any automated machine. To create something in the image of nature is to create a machine, and it was by learning the inner working of nature that man became a builder of machines.-Eric Hoffer, Reflections on the Human Condition Machine learning (ML) is a branch of artificial intelligence that systematically applies algorithms to synthesize the underlying relationships among data and information. For example, ML systems can be trained on automatic speech recognition systems (such as iPhone's Siri) to convert acoustic information in a sequence of speech data into semantic structure expressed in the form of a string of words.ML is already finding widespread uses in web search, ad placement, credit scoring, stock market prediction, gene sequence analysis, behavior analysis, smart coupons, drug development, weather forecasting, big data analytics, and many more applications. ML will play a decisive role in the development of a host of user-centric innovations.ML owes its burgeoning adoption to its ability to characterize underlying relationships within large arrays of data in ways that solve problems in big data analytics, behavioral pattern recognition, and information evolution. ML systems can moreover be trained to categorize the changing conditions of a process so as to model variations in operating behavior. As bodies of knowledge evolve under the influence of new ideas and technologies, ML systems can identify disruptions to the existing models and redesign and retrain themselves to adapt to and coevolve with the new knowledge.The computational characteristic of ML is to generalize the training experience (or examples) and output a hypothesis that estimates the target function. The generalization attribute of ML allows the system to perform well on unseen data instances by accurately predicting the future data. Unlike other optimization problems, ML does not have a well-defined function that can be optimized. Instead, training errors serve as a catalyst to test learning errors. The process of generalization requires classifiers that input discrete or continuous feature vectors and output a class.The goal of ML is to predict future events or scenarios that are unknown to the computer. In 1959, Arthur Samuel described ML as the "field of study that gives computers the ability to learn without being explicitly programmed" (Samuel 1959). He concluded that programming computers to learn from experience should eventually eliminate the need for much of this detailed programming effort. According to Tom M. Mitchell's definition of ML: "A computer program is said to learn from experience E with respect to some class of tasks T and performance measure P, if its performance at tasks in T, as measured by P, improves with experience E." Alan Turing's seminal paper (Turing 1950) introduced a benchmark standard for demonstrating machine intelligence, such that a machine has to be intelligent and responsive in a manner that cannot be differentiated fro...