Machine
A machine uses power to apply forces and control movement to perform an intended action. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems.
Machine Learning
Machine learning is a field of computer science that often uses statistical techniques to give computers the ability to "learn" (i.e., progressively improve performance on a specific task) with data, without being explicitly programmed.
Theory
A theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking. Depending on the context, the results might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.
Theory
The final test of a theory is its capacity to solve the problems which originated it.
George Dantzig (1963) Linear Programming and Extensions, Princeton University Press, p. vii.
Theory
During the period that began with classical Greece and ended with late pagan antiquity, philosophy was more than merely a theoretical discipline. Even when Aristotle identified philosophy with "theory," his purpose is to argue ... that a life of theoretical activity, the life of philosophy, was the best life that human beings could lead.
Alexander Nehamas, The Art of Living (1998)
Theory
If you refuse to take account of theory, then you have forgotten that practice is often an offspring of theory.
Fausto Cercignani in: Brian Morris, Simply Transcribed. Quotations from Writings by Fausto Cercignani, 2014, quote 54.