Scientists work within an elaborate framework of ideas that are subject to testing, evaluation and refinement. Some ideas are discarded when evidence demonstrates that they are untenable, whereas others are supported and gain widespread acceptance. Scientists refer to various types of ideas with different terms—including concepts, theories and paradigms—to distinguish the role the ideas have in the scientific process.
'Concept' is a term that is widely used in everyday English to mean an idea. It has the same general meaning in a scientific context and is often used to refer to an abstract idea. A concept can be exceptionally broad or very specific. For example, 'plants' and 'animals' are both concepts that help scientists, and everyone else, distinguish objects meaningfully in the natural world. 'Mammal' is a conceptual term that refers to a particular type of animal. A concept can be based in experience or may be entirely imaginary; 'music' is an experience-based concept, whereas a 'dragon' is a concept that exists only in the mind.
A theory is a well-established scientific principle that is supported by convincing experimental and observational evidence. A theory has strong explanatory power that helps scientists understand and describe the universe and make predictions about future events. The theory of natural selection, advanced by Charles Darwin in the 19th century, is one of the central organizing principles of evolutionary biology. Einstein's special theory of relativity revolutionized physics in the early 20th century. Other well-known theories in modern science include the geological theory of plate tectonics and the germ theory of disease in medicine.
A paradigm is a central conceptual framework for how you can view the world around you. A paradigm can be so pervasive and broadly accepted as to be almost unnoticed, much the way you don't usually notice the air you breathe. For example, early observers of the heavens assumed that human beings were at the center of the solar system, with other planets and the sun revolving around Earth. That paradigm was eventually overturned by a new view of the solar system that placed the sun at the center. The term 'paradigm' was brought to prominence by the 1962 publication of Thomas Kuhn's influential book "The Structure of Scientific Revolutions." Kuhn argued that science, unlike other disciplines, progressed by broad paradigm shifts in which the entire scientific community comes to accept a new way of thinking about the world.
In addition to concepts, theories and paradigms, scientists also generate ideas known as hypotheses. A hypothesis is a testable idea; it is subject to experimental observation to help determine its validity. Benjamin Franklin's famous kite-flying experiment was a test of his hypothesis that lightning is a form of electrical discharge. A hypothetical idea that is repeatedly tested and found to be reliable may eventually become established as a scientific theory.