The Webster's Dictionary (1953) defines ‘paradigm’ as 'an example, model, or pattern'. But in 1962, the historian of science, Thomas Kuhn, published a book, ‘The Structure of Scientific Revolutions’, in which he adopted the word to refer to the set of concepts and practices that, at any particular period of time, define a scientific discipline.

He defined a ‘scientific paradigm’ as: universally recognized scientific achievements that, for a time, provide model problems and solutions for a community of practitioners, including:

• what is to be observed;
• the types of questions that can be asked;
• how these questions are structured;
• the predictions made by the primary theory within the discipline;
• how results should be interpreted;
• and how an experiment is to be conducted.

Most scientists never question the paradigm. They solve problems whose solutions reinforce and extend the scope of the paradigm rather than challenging it, and when phenomena are observed that the paradigm cannot account for—or even contradict it—they are often ignored. However, when anomolies accumulate sufficiently, they trigger a paradigm shift, in which scientists abandon the old paradigm for a new one.

Kuhn argued that science does not progress in a linear and continuous way, but scientific fields undergo periodic ‘paradigm shifts’, which open up new approaches to understanding what would never have been considered valid before.

He also argued that the notion of scientific truth at any given moment, cannot be established solely by objective criteria, but is defined by a consensus of a scientific community. This brought personality, subjectivity, power and money into the mix, far from the dispassionate and orderly progress of observation and experimentation, in the light of ‘reason’, envisioned since the beginning of the ‘Age of Reason’ in the 17th century.

It is interesting that Kuhn's ideas aroused great interest, yet many thinkers had proposed similar critiques in the past and been ignored:

Take for instance, the statement by the logician Quine, in ‘Two Dogmas of Empiricism’ (1953), that describes the sum of all accepted human knowledge as a vast field, with basic concepts isolated and protected from reality in the centre, with interaction with reality restricted to the edges, where recalcitrant experience is routinely put down to error or hallucination. It says basically the same thing as Kuhn, but did not make waves in the scientific establishment. (Link)

Or you could go back to 1605, when the father of empirical observation and method, Francis Bacon, noted that whilst the sylogism (deductive logic), was useful in imparting activity to the sciences, it could never achieve the subtlty of nature. (Link)

Years later, Kuhn began to focus on the semantic aspects of scientific theories, the taxonomic structure of scientific terms, and abandoned the 'change of paradigm' concept for a change in the taxonomic structure of the theoretical language of science. This analysis seems quite euphamistic when one considers the extent of power and spite that over the centuries have characterised the processes by which scientific paradigms have defended themselves from attack:

Ignaz Philipp Semmelweis, in the 19th century, died in a lunatic assylum after he advocated that doctors should wash their hands with antiseptic solution before treating patients. Link

Alfred Wegener proposed the hypothesis that the continents are slowly drifting around the Earth—continental drift. It was widely rejected by mainstream geology until the 1950s—20 years after his death. Link

Galileo Galilei championed Copernican heliocentrism—that the Earth rotates daily and orbits around the sun. He was tried by the Inquisition, found ‘vehemently suspect of heresy’, forced to recant, and spent the rest of his life under house arrest. Link

A related concept is Michel Foucault's ‘episteme’. A more generalised concept, it can be seen to subsume the scientific paradigm into the processes of thought creation and maintenance characteristic of an age. See article Link.

SOURCES

https://en.wikipedia.org/wiki/Thomas_Kuhn

https://www.thelivingphilosophy.com/kuhn-paradigm/

https://en.wikipedia.org/wiki/Paradigm_shift

https://www.simplypsychology.org/Kuhn-Paradigm.html

https://probaway.wordpress.com/2013/10/14/philosophers-squared-thomas-kuhn/

https://en.wikipedia.org/wiki/Ignaz_Semmelweis

https://en.wikipedia.org/wiki/Alfred_Wegener

https://en.wikipedia.org/wiki/Galileo_Galilei