This article describes some conceptual terminology used by scientists. Confusion often results from using scientific terms inappropriately.
a) Any recorded piece of information, about a phenomenon, is DATA. It can be the result of an observation or an experiment; it can be qualitative or quantitative. It can be published or not.
b) A piece of data recognized as valid, by most practitioners in a given field, becomes a FACT. Facts are data that are reproducible; any scientist using the same protocol is expected to obtain the same data; at a specified level of reproducibility. Science is not mathematics; that is why the level of reproducibility, for example 90%, should be reported.
c) A LAW is a generalization of facts. I am thinking about Kepler's Laws (how planets move), about Mendeleev's Law (how elements are ordered in a chart), Faraday's Law (how electric currents can be magnetically induced), etc.
d) A THEORY is an explanation of a law. I am thinking about Newton's gravitational theory, about Maxwell's equations, about quantum mechanics, etc. Distinctions between laws and theories (and between facts and theories) are worth recognizing. Unfortunately, this is not always done.
e) Theories are based on assumptions, which may or may not be valid. Assumptions can be based on facts, on laws, or on intuition.
f) We like scientific theories not only because they are logically (mathematically) correct but also because they might lead to useful discoveries. Scientific theories evolve; some are more powerful, more general, and more elegant, than others.
g) The concept of "absolute truth,' often used by mathematicians and theologians, does not belong to science. Wade wrote: "A theory, however strongly you believe it, inherently holds a small question mark. The minute you erase the question mark, you've got yourself a dogma."
h) A hypothesis is a tentative idea to be confirmed. It is a common instrument of human thinking. Hypothesizing is used by all those who collect data, who validate data, who generalize from available data, and by those who explain facts of nature. Tentative assumptions are made by all thinking people, not only by physical scientists.
P.S.
Nearly all experimental reports, in my opinion, are data rather than facts. A single experimental result, even when reported by a reputable scientists, can be erroneous. Here is one illustration. Last summer I was leading an attempt to validate a claim made by a well respected electrochemist. Four people were independently using the same experimental protocol. But our attempts to validate the claimed discovery were not successful. Our article will be published in a reputable scientific journal.
Ludwik Kowalski (PhD) (see Wikipedia)
I have been conducting scientific research for several decades and I know that misunderstandings often result from inappropriate use of terminology.
By Ludwik_Kowalski