reference link for the difference between pseudo and quasi at pseudo, quasi and semi

Thanks to stack exchange [users] for making it clearer. Meanwhile, i found another useful blog defining the terms while making the differences: Non-science, pseudoscience, quasi-science and bad science; is there a difference?

  • semi = half; I have never heard of "semi-science", but "semi-monthly" means twice a month (once every half month).
    – GEdgar
    Commented Jan 18, 2016 at 21:27
  • Can you clarify in your post exactly what your question is?
    – Mitch
    Commented Feb 6, 2016 at 13:39

2 Answers 2


Each would carry a different meaning, except for "semi." I've never heard anything called "semi-science." I don't know what that would even mean.

Using "pseudo" beforehand would mean trying to be like science. Using "quasi" beforehand would mean almost but not quite science. Pseudoscience would mean it's dressed up as science, masquerading as science. Quasi-science would not quite meet the standards of science but would also not necessarily be trying to pass itself off as science. A pseudoscience could be a quasi-science and vice versa, but the connotation of each prefix results in somewhat different implications.

If you're looking for a word that doesn't have the baggage of either of these two words, you might try "soft science." Economics, for example, is described as a soft science. Another term you might want to look into is "parascience."


A pseudoscience is a false science, a discipline masquerading as science without its discipline. From the Greek *ψευδής (pseudes), meaning false. Scientists generally use the prefixes para-, quasi-, and semi- to mean the same thing as pseudo-, but the first three prefixes have a long history and are used, especially by non-scientists, with different meanings.


  • para-, aside from science, even above and beyond. The study of things not addressable by science.
  • quasi-, an admixture, partly science, possibly extendable to be fully scientific
  • semi-, a joining of discernible scientific parts and non-scientific parts

Parascience has an old and distinguished pedigree. The Ngram viewer find its use in the journal Nature from 1869 by Sir Norman Lockyer, Fellow of the Royal Society, astronomer and co-discoverer of helium:

Parascience has all the qualities of a magical system while wearing the mantle of science. Until any significant discoveries are made, science can justifiably ignore it, but it is important to say why: parascience is a pseudo-scientific system....

Sir Norman clearly means to denigrate the parascientific, equating para- with pseduo-, but its later users take the prefix to mean alongside or even beyond. Thus from the journal Systematics (Volume 9, 1971)

It is the Change which changes and transforms all things including birth and death. The Change according to the I Ching, the standard work of parascience, is the ultimate, which transcends the category of our description.

Parascience has subcategories -- parapschology, the paranormal, etc. -- the proponents of which all claim some reliable basis for their field.

Semiscience dates from the same era, and we find in the journal The Sanitarian from 1882:

I have no patience with the cold cruelty of semiscience which calmly contemplates the preventable sickness and death, and hails these as weeding and pruning processes by which to make the race better and stronger.

The article discusses the efficacy of "sanitary science," which includes fighting disease with vaccination, antisepsis, etc. The prefix semi- comes from the Latin for half, but its meaning encompasses "partly" or "almost." Here the reference is to the eugenic view of social darwinism that joins one part science (i.e., Darwin's natural selection) to one part social philosophy of non-interventionism.

We can get a more modern flavor of the semiscience from Cosmology and Controversy: The Historical Development of Two Theories of the Universe (1999) by Helge Kragh, which reflects on the discussion of whether the study of the universe as a whole can ever be truly science. This argument goes back at least to 1953, when scientists G. Whitrow and H. Bondi considered in British Journal for the Philosophy of Science whether science was up to the task of explaining a unique object (i.e., the universe). Kragh writes:

This uniqueness had made cosmology "a borderline subject between the special sciences and philosophy," and Whitrow believed that it would remain such a borderline semiscience.*

Quasiscience is even older, finding a home in a book review in Economist: Weekly Commercial Times, Banker's Gazette and Railway Monitor (Volume 4, 1847), in which the reviewer regards the book as

... well worthy of being studied, though we should have liked it much better had it been founded wholly on the ideas and knowledge which the peculiar circumstance and condition of the Unites Staes call into being, instead of being founded on a quasi-science of Europe.

The topic is natural rights and property law, and the book apparently bases its conclusion on phrenology, the above-mentioned "quasi-science." A more modern usage occurs in Nonsense on Stilts: How to Tell Science from Bunk (2010) by Massimo Pigliucci:

Thus the demarcation problem remains, and throughout this book we examined many of it facets, looking for insights from the history of science, discussions about the alleged difference between soft and hard science, and critical analyses of quasi-science and downright pseudoscience.

Quasi- as a qualifier can mean "only apparently" or "partly." In the first cite, phrenology was probably considered partly science, a field which might become fully scientific. It's likely Mr. Pigliucci leans toward the "only apparently" view.

* Forgive me for not following the trail to the BJPS, which is behind a paywall.

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